JPS6327694B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention is a so-called electrochromic device (hereinafter referred to as EC) that exhibits reversible color development and decolorization upon application of voltage.
The present invention relates to elements, and more specifically relates to solid-state transmission type EC elements.

Conventionally, several EC elements using tungsten oxide thin films have been proposed.

It is generally explained that this is because a color center is formed by the following reaction when the tungsten oxide thin film side is negatively biased.

WO ₃ (colorless) +XM ⁺ +xe→MxWO ₃ (blue) Here, M ⁺ is a proton, an alkali metal ion,
Indicates silver ion. Such EC elements are broadly classified into solution type and solid type. The former has a display electrode and a counter electrode facing each other and a liquid electrolyte is filled between them, and has relatively good characteristics such as color density and response speed, but has the drawback that the structure that seals the electrolyte is difficult and reliability is poor. There is.

The latter has a display electrode and a counter electrode facing each other, with a solid ion-permeable insulating film interposed therebetween.

Solid systems can generally overcome the difficulties of liquid systems, but
It has the disadvantage that color density and response speed are slow.

The configuration of the conventional example will be explained below based on the drawings.

FIG. 1 shows a transparent substrate 11 having a transparent conductive film 12.
Tungsten oxide is laminated on top as the display electrode 13, and CaF ₂ is laminated as the ion-permeable insulating film 14.
A thin film of Au is used for the counter electrode 15. This device uses a thin Au film for the counter electrode 15, so it has poor transmittance, and since there is no reversible process for the reaction of the counter electrode 15, gas is generated and the device has a short lifespan. .

FIG. 2 shows a transparent substrate 21 having a transparent conductive film 22.
A tungsten oxide film is placed on top as the display electrode 23,
In addition, RbAg ₄ I _5, which is a conductor of Ag ions, is laminated as the ion-permeable insulating film 24, and Ag is deposited on the counter electrode 25.
It uses a thin film of In this device, the reaction Ag→Ag ⁺ +e occurs at the counter electrode, so the charge balance is maintained, but RbAg ₄ I ₅ is unstable, and Ag ions are discharged at the display electrode and precipitate in the form of dentrite. There are also disadvantages of slow response due to the large size of Ag ions.

FIG. 3 shows a transparent substrate 31 having a transparent conductive film 32.
On top, tungsten oxide is placed as a display electrode 33.
Further, chromia is laminated as the ion-permeable insulating film 34, and an Au film is used as the counter electrode 35.
In this element, protons emitted from the water in chromia act as charge carriers.
This element also had the disadvantage of low transmittance because it used an Au film for the counter electrode.

In view of the current state of solid-state devices as described above, the inventors of the present invention have conducted various studies and found that a transparent conductive film allows reversible inflow and outflow of positive ions and electrons in an amount that compensates for their charges. A crystalline EC thin film with virtually no change in optical properties in the visible range, an ion-permeable insulating film, and the reversible entry and exit of cations and electrons in an amount that compensates for their charge, thereby making it possible to maintain optical properties in the visible range. The above drawbacks are solved by creating an element that includes at least a laminated structure of an EC thin film whose optical properties change and a transparent conductive film.

FIG. 4 shows an example of a solid-state transmission type EC element according to the present invention, in which cations and an amount to compensate for their charges are placed on a transparent substrate 41 on which a transparent conductive film 42 of indium oxide, tin oxide, etc. is formed. A crystalline EC thin film 43 is formed as a counter electrode in which electrons reversibly enter and exit, but the optical properties in the visible range do not substantially change.

The crystalline EC thin film 43 has the following properties.

(1) It has a porous structure that allows ions to diffuse by controlling the potential.

(2) It has such mobility that electrons that compensate for the charge of the diffused ions drift and reach the vicinity of the ions.

(3) The mother lattice, ions, and electrons interact to form a color center.

(4) It has crystallinity such that electrons trapped in the color center can be delocalized to a considerable degree;
Color centers have no absorption in the visible range.

Such crystalline EC thin film 43 is made of tungsten,
Although it can be formed from an oxide or sulfide of molybdenum, vanadium, chromium, manganese, niobium, or tantalum, it is most preferably a crystalline tungsten oxide film having a porous structure. To explain the formation method using tungsten oxide as an example, first, tungsten oxide is vapor deposited at a vacuum level of 1×10 ^-4 to 5×10 ^-3 Torr, more preferably 5×10 ^-4 to 2×10 ^-3 Torr. A porous tungsten oxide amorphous thin film is formed by heating, and then heat-treated at a temperature of 350°C to 450°C to form a porous crystalline thin film.

Crystalline EC formed in this way as a counter electrode
On the thin film 43, an insulating film 44 is formed that allows cations to pass through but substantially does not allow electrons to pass therethrough. Such ion-permeable insulating film 44 may be made of known materials, such as calcium fluoride, lead fluoride, silicon oxide, chromia, β-alumina, lithium nitride, lithium aluminate, lithium silicate, lithium zinc germanate, etc. Lithium magnesium germanate is used.

On such an insulating film 44, there is an EC thin film 45 as a display electrode in which cations and electrons in an amount that compensates for their charges can reversibly enter and exit, and the optical properties in the visible range change thereby. By forming the transparent conductive film 46, the transmission type EC element of the present invention can be obtained.

When the EC thin film 45 serving as a display electrode is negatively biased, it takes in cations and electrons in an amount that compensates for their charge, and forms a color center through interaction with the mother lattice, cations, and electrons. Examples include oxides and sulfides of tungsten, rhenium, vanadium, niobium, tantalum, chromium, manganese, and titanium, but preferably an amorphous thin film containing tungsten oxide is used.

In order to operate the transmission type EC element of the present invention reversibly, in advance, either the crystalline EC thin film 43 as a counter electrode or the EC thin film 45 as a display electrode is charged with cations and an amount of electrons to compensate for the charge. need to be injected. From the viewpoint of the manufacturing method, it is desirable to inject cations and electrons into the crystalline EC thin film 43 as the counter electrode, and as described above, the crystalline EC thin film 43 as the counter electrode is injected onto the transparent substrate 41 having the transparent conductive film 42.
A thin film 43 is formed, and in this state it is immersed in an electrolyte containing cations and a voltage is applied to inject it.

As an example, for the crystalline EC thin film 43 as a counter electrode.
Taking as an example a device constructed using crystalline tungsten oxide with a porous structure into which Li ions and electrons are injected, and using an amorphous tungsten oxide thin film 45 as a display electrode, the transmittance characteristics when operated are shown in Table 5.
This will be explained based on the diagram.

When no voltage is applied, the spectral curve of the EC thin film 45 as a display electrode is shown in FIG. 51, and the spectral curve of the crystalline EC thin film 43 as a counter electrode is shown in FIG. 52, which is a transmission type element. When a voltage is applied so that the display electrode side of such an element is negative and the counter electrode side is positive, the crystalline EC thin concentration 43 on the opposite electrode side liberates Li ions according to the following formula: LixWO ₃ →xLi ⁺ +xe+WO ₃ . EC thin film as display electrode 4
5 forms xLi ⁺ +xe+WO ₃ →LixWO ₃ LixWO ₃ by the reaction of the following formula, and is colored blue. The spectral curve at this time is shown in FIG. 5.

Next, when a voltage is applied so that the display electrode side is positive and the opposite side is negative, a reaction opposite to the above occurs, resulting in a transmission type element.

As mentioned above, since reversible exchange of electrons occurs between the EC thin film serving as the display electrode and the EC thin film serving as the counter electrode, charge balance is maintained and deterioration is prevented.

Furthermore, in the transparent state, the transmittance is excellent because a transparent conductive film is used instead of the conventional thin Au film.

Furthermore, since it is a transmissive type, it is possible to display an easy-to-read display using illumination from the rear or side, and it is also possible to increase the display contrast by arranging a reflective plate or a color background plate at the rear.

In addition to display devices, applications include curtainless windows as light modulating glass, anti-glare mirrors for automobiles,
Of course, it can be used in sun visors with variable light intensity, glasses with adjustable light intensity, and the like.

[Brief explanation of drawings]

1 to 3 are side views of a conventional EC element, FIG. 4 is a side view of a transmission type EC element of the present invention, and FIG. 5 is a diagram showing a spectral curve. 11, 21, 31, 41...transparent substrate, 12,
22, 32, 42, 46...transparent conductive film, 13,
23, 33... Display electrode, 14, 24, 34... Insulating film, 15, 25, 35... Counter electrode, 43... Crystalline EC thin film, 44... Ion-permeable insulating film, 45
...EC thin film.

Claims (1)

[Claims] 1. A transparent substrate, a transparent conductive film disposed on the substrate,
a crystalline electrochromic thin film in which cations and electrons reversibly enter and exit in an amount that compensates for their charge, but whose optical properties in the visible range remain substantially unchanged;
The above-mentioned insulating film allows cations to pass through but does not substantially allow electrons to pass through, allowing reversible entry and exit of cations and electrons in an amount that compensates for their charge, and this changes the optical properties in the visible range. A transmission type electrochromic element comprising at least a laminated structure of an electrochromic thin plate and a transparent conductive film. 2. The transmission type according to claim 1, wherein the crystalline electrochromic thin film whose optical properties do not change in the visible range is a crystalline thin film containing tungsten oxide and having a porous structure sufficient for ions to enter and exit. Electrochromic device. 3. Claim 1 or 2, wherein the electrochromic thin film whose optical properties in the visible range change is an amorphous thin film containing tungsten oxide and having a porous structure sufficient for ions to enter and exit.
Transmission type electrochromic device as described in .