JPH0241724B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to an electrochromic device (electrochromic device).
-chromic device), that is, a display device that changes color when a voltage is applied, and a method for manufacturing such an electrochromic device.

The present invention includes a first electrode and a metal-sensitive compound in contact with the first electrode and in contact with a solid fast ion conductor.
The fast ions in the fast ion conductor are ions that dissolve in the metal-sensitive compound and change its color, and the ion conductor itself has a second layer that can donate the same ions as the fast ions of the conductor.
Relating to electrochromic devices in contact with electrodes.

In this specification (including the claims),
"Metal-sensitive compound" means a compound that is capable of dissolving metal atoms and changing color while doing so. In electrochromic devices of the type to which the present invention relates, the metal atoms of interest are, of course, the same as those produced by the discharge of fast ions in a solid fast ion conductor.

[Conventional technology]

Electrochromic devices of the type described above (hereinafter referred to as ``electrochromic devices of the type defined above'') are covered by published British Patent No.
Nos. 1540713 and 1540714 and pending British Patent Application No. 28241/76 (UK Patent No. 2081922), the general contents of which are disclosed in Japanese Patent Application Publication No. 10449/1983. All of these patents and patent applications relate to inventions made by the inventors of this invention.

In the scientific literature published by the same above-mentioned inventors, a number of factors regarding the materials, dimensions and other parameters of the materials used in electrochromic devices, alone or in combination with other factors, are as follows: Disclosed.

“Thin Film Electrochromic Display Based on Tungsten Bronze”, Thin Solid Films, 38 (1976)
86−100; “Solid State Electrochromic
Cell-R _b A _g4 I ₅ /WO ₃ series” Thin Solid Films, 24 (1974) S45-S46; “Solid State Electrochromic
Cell: Na-β-alumina/WO ₃ system” Shin Solid Films, 40 (1977) L19-L21; “Optical and electrical properties of electrochemically colored WO ₃ thin films” Electrosimica Acta ( Electro-chimica Acta) 1977 Volume 22, PP751-
759; “Atomic motion in tungsten bronze thin films” Thin Solid Films, (50 (1978) 145-
150; and “Changes in the chemical potential of sodium in Na ₂ WO ₃ thin films,” Thin Solid Films, 62
(1979) 358−387.

These publications are cited to provide background information to assist those skilled in the art in the manufacture and operation of electrochromic devices in accordance with the novel features of the present invention as described below.

[Problem to be solved by the invention]

The present invention relates to an improvement in the electrochromic device described above, and an improvement in the method for manufacturing this device.
The present invention relates to a number of parameters of an electrochromic device as described above, and further to the interrelationship of these parameters both in the final finished electrochromic device and in the method of manufacturing the device. As will become apparent from the description below, although some relevant factors have been disclosed in publications by the inventors, and the importance of some of these factors has actually been mentioned, the present invention derived from the special, novel and non-trivial correlation of these factors and the optimization of a certain number of preferred ranges of the parameters. Although the known devices described in the above-mentioned patents have reached the stage of experimental operation, some problems remain in the production and use of practical commercial specimens, and the present invention is directed to the production and operation of such commercial specimens. problems that can be solved or significantly reduced.

In particular, in at least a preferred embodiment,
The present invention relates to improvements in the stability of electrochromic devices during the manufacturing process of the device and subsequent use of the device. The invention also particularly relates to improving the stability of electrochromic devices. The invention also particularly relates to reducing the time required to induce a desired color change in an electrochromic device, thereby reducing the "write" time of the device when such an electrochromic device is used for display purposes. It is possible to provide a device in which the time is significantly reduced and which continues to operate with relatively short "write" times over long periods of operation. None of the above-mentioned prior publications teach the specific combinations and interrelationships of factors encompassed by this invention that produce these favorable results.

[Means to solve the problem]

The present invention comprises a first electrode and a layer of a metal-sensitive compound in contact with the first electrode and in contact with a solid fast ion conductor, wherein the fast ions in the fast ion conductor are dissolved in the metal-sensitive compound and its color The fast ion conductor itself is a second ion that can donate the same ions as the fast ions of the conductor.
In an electrochromic device in contact with an electrode, the metal-sensitive compound is (i) substantially stoichiometric; (ii) substantially free of water; (iii) in the range of 40 Å to 250 Å. and (iv) a layer thickness in the range of 0.2μ to 2μ.

In this specification (including the claims),
“Substantially stoichiometric” as one qualitative criterion
By this we mean that the metal-sensitive compound is sufficiently stoichiometric that no residual coloration occurs due to the absence of atoms or molecules from the crystal structure. In other words, if there is no intentional coloration of the metal-sensitive compound by insertion of metal atoms into interstitial positions, the metal-sensitive compound will be used in the layer used in the device, in the ordinary sense of the term in the display field. The thickness of the material must be transparent or colorless.

In this specification (including the claims),
“Substantially stoichiometric” as a quantitative criterion
means that when the metal-sensitive compound consists of a crystalline oxide thin film structure, the number of oxygen atoms lost from the crystal structure is not more than 10 ¹⁵ per square centimeter of the film.

In this specification (including the claims),
As one qualitative criterion, "substantially free of water" means that the metal-sensitive compound is substantially free of water due to conduction paths along the grain boundaries in the metal-sensitive compound, i.e., during the diffusion of atoms in the metal-sensitive compound. This means that it does not contain enough water to eliminate molecules that would interfere with the conduction paths between the moving particles.

In this specification (including the claims),
As one quantitative criterion, "substantially free of water" means that the metal-sensitive compound has less than 1 mole percent water, preferably less than 0.5 mole percent water.

that the material is stable to annealing to larger particles due to a qualitative criterion of average particle size in the metal-sensitive compound;
It is also preferable that the substance is stoichiometric, and that the average particle size is made as small as possible without contradicting the stoichiometric nature of the substance. In one embodiment, when the device is manufactured by vapor deposition or sputtering of a metal-sensitive compound, the metal-sensitive compound is stable in use and is stoichiometric during the deposition process of the material. It is preferred to have an average particle size as small as possible unless consistent with this.

By quantitative criteria of average particle size, it is preferred that the metal-sensitive compound has an average particle size in the range of 40 Å to 100 Å, most preferably 45 Å to 75 Å. A particularly preferred average particle size is about
It is 50 Å. Another particularly preferred average particle size is about 60 Å.

Various qualitative criteria for the thickness of the metal-sensitive compound layer dictate that the metal-sensitive compound layer be thin enough to be transparent, thin enough to be stoichiometric (e.g. (sufficiently thin to be stoichiometric during deposition of the metal-sensitive compound during device fabrication); and resistant to intentional color development of the metal-sensitive compound due to diffusion of atoms into the compound. It is preferably thin enough to prevent unwanted metal deposition therebetween. However, it is preferred that the metal-sensitive compound is thick enough to accommodate an adequate flow of atoms diffusing into the individual particles during the intentional color development of the metal-sensitive compound during use.

Depending on the stoichiometric criteria for the thickness of the metal-sensitive compound layer, the layer thickness may range from 1μ to 0.5μ, preferably
It is preferably in the range of 0.75μ to 0.5μ.
A particularly preferred layer thickness value is approximately 0.6μ.

According to another aspect of the present invention, a step of attaching a metal-sensitive compound to at least a portion of one side of a substrate of a fast ion conductor containing, as fast ions, ions of a metal that changes color when dissolved in a metal compound; depositing a first electrode on at least a portion of the metal-sensitive compound to prevent direct contact between the electrode and the fast ion conductor; and depositing fast ions on at least a portion of the other side of the substrate of the fast ion conductor. In a method for manufacturing an electrochromic device comprising the step of depositing a second electrode capable of donating the same ions as the fast ions of the conductor, the step of depositing a metal-sensitive compound comprises (i) making the deposited substance stoichiometric; depositing the metal-sensitive compound with a sufficiently low deposition rate; (ii) depositing the metal-sensitive compound from a substantially water-free compound source in a substantially water-free atmosphere; (iii) metal-sensitive (iv) depositing the metal-sensitive compound in a layer having a thickness of 0.2μ to 2μ; Provided is a method for manufacturing an electrochromic device, comprising the step of depositing at a speed and time sufficient to achieve the desired results.

The criterion of "substantially stoichiometric" is the same as that described above for electrochromic devices according to the invention.

In this specification (including the claims),
One criterion, "deposited in a water-free atmosphere from a water-free compound source" means that when a metal-sensitive compound is deposited, it must be deposited in accordance with one or more of the criteria specified for the apparatus embodiment of the present invention. Means substantially free of water.

In this specification (including the claims),
One standard, ``water-free compound source of metal-sensitive compounds,'' means that the raw materials for metal-sensitive compounds are 1
This means that it must have a moisture content of less than mol%.

In this specification (including the claims),
One criterion, "water-free atmosphere" means that the atmosphere to which the metal-sensitive compound is deposited has a moisture content of 10 ^-7 torr or less.

The deposition rate of the metal-sensitive compound is preferably between 10 Å and 100 Å per second, and most preferably between 20 Å and 40 Å per second.

The rate and time of deposition of the metal-sensitive compound is preferably carried out at a rate of 20 to 40 Å per second for a time in the range of 2 to 4 minutes, and about 30 Å per second.
More preferably, it is carried out at a speed of about 3 minutes.

The rate and time of deposition of the metal-sensitive compound, and other conditions of the method, such that the average particle size of the metal-sensitive compound and the layer thickness fall within one or more of the preferred ranges specified for the above embodiments of the invention. It is preferable to set it so that it is within the range.

Considering the preferred composition of the electrochromic device as defined above and in accordance with the invention, the metal-sensitive compound is an oxide of a transition metal, in particular tungsten oxide (WO ₃ ), molybdenum oxide (MoO ₃ ) or Solid solutions of these and other transition metal oxides in their highest oxidation state are preferred. Such oxides dissolve metal atoms, especially monovalent atoms such as atoms of alkali metals (eg potassium, sodium and especially lithium), copper or silver, and can change color during dissolution. The most common color change is colorless to blue. Other metal-sensitive compounds that may be cited include oxides of titanium and zirconium and their suitable solid solutions. The color change of these oxides upon dissolution of the metal atoms is reversible; in the electrochromic device of the present invention, reversal of the voltage that originally produced the color causes the color to disappear.

The use of a solid fast ionic conductor as the electrolyte is an essential feature of the electrochromic device defined above. As already explained, the fast ions in the electrolyte, when released, must be capable of producing atoms that dissolve in the metal-sensitive compound and cause it to change color. This means that the fast ions of the fast ion conductor are preferably selected as alkali metal, copper or silver ions.

The fast ionic conductor is preferably 1×10 ⁶ ohm.
have a resistivity of less than or equal to 1×10 ⁴ ohm-cm, most preferably less than or equal to 1×10 4 ohm-cm, and conduct electricity only by ionic conduction of ions of the metal to be inserted into the metal-sensitive compound. It must be a substance. For convenience of use, the fast ion conductor is preferably made of a material that can be deposited, cast or otherwise formed into a sheet or plate. It may not react with or in the atmosphere to which it is exposed (as is the case for all components), or may be protected from an atmosphere that would cause an undesirable reaction (as is the case with all components of the device). It has to be something. Such protection may be effected, for example, by encapsulation to prevent chemical reactions, or by filtration to prevent or reduce exposure to radiation such as sunlight if this is undesirable.

An example of a suitable fast ionic conductor is given in British Patent No.
1540713, and examples of silver-containing fast ion conductors are halogenated (especially iodized) complexes of silver with alkali metal or quaternary ammonium ions.

Other fast ion conductors that may be used are copper-containing fast ion conductors, which are also described in GB 1540713.

However, alkali metal containing fast ion conductors such as sodium-β-alumina, lithium-β-alumina and potassium-β-alumina are preferred as fast ion conductors for use in the present invention. These include Na ₂ O, Li ₂ O or
It is a mixed oxide of K ₂ O and Al ₂ O ₃ . Typically they contain 5 per molecule of alkali metal oxide.
Contains between 1 and 11 aluminum oxide molecules. A particularly preferred fast ion conductor is lithium-β-alumina.

Other fast ion conductors are described as "ion-conducting crystals" in US Pat.

Preferably, the fast ion conductor is white or colorless, or may be of another color, in which case the color is selected to provide a suitable contrast between the metal-sensitive compound and its at least one colored state. It is often advantageous to use a background body separate from the metal-sensitive compound that can provide a suitable contrast with the metal-sensitive compound if the fast ion conductor is transparent. Such a background body may be the second electrode. The second electrode can also be silver plated to provide mirror-like contrast.

Thus, in accordance with a preferred embodiment, the solid fast ion conductor is transparent and positioned so as to provide a background for the color development of the layer of metal sensitive compound when viewed by placing the solid fast ion conductor behind the layer of metal sensitive compound. can.

According to an alternative format, one of the electrodes is optically reflective and the metal-sensitive compound, solid fast ion conductor and other electrodes are optically transparent in the absence of intentionally produced coloration during operation of the device. It can be arranged as follows. The arrangement is such that an optically reflective electrode is placed at the rear of the device to provide a mirror effect when viewed in the absence of intentional color development.

In the electrochromic cell of the present invention,
Application of a voltage across a solid electrolyte formed of one of the fast ion conductors described above causes fast ions to be ejected and the resulting metal atoms to be dissolved in the metal-sensitive compound. It is this process that causes the metal-sensitive compound to develop color. Similarly, voltage reversal causes the metal in the metal-sensitive compound to migrate as ions into the fast ionic conductor. In order to maintain its equilibrium in the fast ion conductor, the electrode in contact with the fast ion conductor, referred to above as the second electrode, must be able to donate and accept fast ions. If the fast ions are silver or copper, the second electrode may itself be made of silver or copper. Furthermore, since the amount of metal atoms involved in the operation of the electrochromic cell of the present invention is very small, these electrodes can themselves be made very small without fear of inadequate supply of metal ions, but the dimensions varies over a very wide range. The minimum area that can be used in a particular case is readily determined by a single test. If the fast ion conductor contains ions of alkali metals such as sodium, lithium or potassium as fast ions, it is difficult to make the second electrode with an alkali metal due to the well-known reactivity of these elements in the free metal state. is usually unfavorable. However, the second electrode can be made of a suitable bronze, for example of the general formula M _x WO ₃ , where M is, for example, lithium, sodium or potassium, and x preferably has a value between 0.05 and 0.5. Such materials can release metals as corresponding metal ions to the fast ion conductor. A ferrite consisting of a suitable ion can also be used as the second electrode, for example lithium ferrite. Other suitable materials, alloys or compounds may be used as well. Many substances e.g. U.S. Patent No. 3971624
No. 3, it is described as being suitable for the non-polarizable electrodes described in that patent.

It is desirable that at least one of the electrodes be transparent to visible light to facilitate observation of the color changes that occur. This can be achieved by using a suitable transparent electrode material, such as indium-tin oxide, as the first electrode in contact with the metal-sensitive compound.

Electrochromic devices can be made entirely of solid materials. It will be appreciated that this is an important practical advantage and provides good strength and stability during use. Furthermore, it can be configured in a manner suitable for rapid response to relatively small applied voltages, on the order of 1 volt.

Considering the various items of the prior art listed above in relation to the features of the present invention explained above,
First of all, it is noted that the importance of the stoichiometric properties of metal-sensitive compounds and the water-free requirements for the compounds has hitherto not been recognized. In the example of a conventionally produced electrochromic cell, the metal-sensitive material is e.g.
Although made transparent, as in No. 1540713,
This was achieved for relatively large particle size films. The manufacturing techniques described in this patent result in average particle sizes on the order of 50 Å. The requirements involved in producing films of small particle size while maintaining sufficient stoichiometry of the material to preserve optical clarity of the material were heretofore unrecognized.

Similarly, although previously conducted experiments have yielded electrochromic devices with relatively small average particle sizes, the benefits to be derived from particle size in terms of diffusion of ions into metal-sensitive substrate materials are limited. The manufacturing technology is carried out in the presence of water,
This was ignored because it caused blockage of conduction paths along grain boundaries.

Shin Solid Films in the above publications;
40 (1977) L19-21 states that the primary cause of device failure in the electrochromic devices defined above is the presence of deep holes in the beta-alumina to which tungsten trioxide adheres. Avoid direct contact between the electrodes of the electrochromic device and the fast ionic conductor to prevent leaching of the metal that is intended to be dissolved in the metal-sensitive material, as described below. This is very important. This paper discusses some manufacturing techniques related to the method of the present invention.

Among the above publications, Electro Simica Acta,
Volume 22, page 75 contains a discussion of the role of grain boundaries in the diffusion of metal ions into metal-sensitive materials; rapid diffusion to grain boundaries may be followed by slow diffusion to crystallites. , it is stated.

Among the above publications, Shin Solid Films,
50 (1978) 145-150 describes general precautions for the production of tungsten trioxide without significant amounts of water and water in the commonly supplied tungsten trioxide, but without water. There is no teaching as to why tungsten trioxide is required.

Among the above publications, Shin Solid Films,
50 (1978) 145-150 discusses the influence of the texture of tungsten trioxide films on the diffusion of metal atoms into such metal-sensitive compounds, but this academic discussion is not defined by the present invention. No effective proposals have been made for specific electrochromic devices. In particular, no teachings are found in this report regarding the correlation between low average particle size and actual electrochromic device manufacturing techniques and other manufacturing techniques and other parameters.

Regarding the feature of the present invention regarding the thickness of the layer of optically responsive metal-sensitive compound, the above-mentioned thickness criterion provides a relationship between thickness and metal-sensitive compound that is quite different from the relationship expected from proposals in the prior art. It is based on the recognition of the relationship between diffusion into the All publications relating to electrochromic devices of the type described above emphasize the need for very thin films of metal-sensitive compounds. For example, pending British Patent Application No. 28241/76 (UK Patent No. 2081922) states that the thickness of the metal-sensitive compound is 1μ or less, conveniently from 1 to 0.01μ.
The thickness is preferably between 0.5 and 0.05μ. Particularly preferred is a thickness between 0.5 and 0.2μ. It is generally assumed in the prior art that the rate of diffusion of metal atoms into a substrate metal-sensitive compound is increased by making the layer of metal-sensitive compound as small as possible, consistent with the actual manufacturing technique and device construction. was. However, it has been discovered by the present invention that the optimum thickness is not simply as small as possible, but depends on a number of interrelated factors. An important one of these factors is that the rate of diffusion of metal atoms into the base metal-sensitive compound is not necessarily always increased by decreasing layer thickness. The diffusion coefficient is a function of the concentration gradient of the atoms in the particles of the metal-sensitive compound and, within limits, the thicker the film of the metal-sensitive compound, the faster the atoms diffuse into the material. It has been established that it is fast. For practical display devices, this means that, within limits, the thicker the layer of metal-sensitive compound, the faster the "write" time to produce the intended color development of the electrochromic device.

The explanation for this phenomenon is believed to involve the diffusion of two parts of the atom into the metal-sensitive compound.
The movement of atoms across grain boundaries is very fast, while diffusion into individual grains is slow. Some of the atoms diffuse into the particle, where a large concentration gradient occurs within the particle since there are no metal atoms in the center of the particle and a large concentration of atoms near the periphery. This creates an electric field within each particle, the effect of which is that the value of the diffusion coefficient itself depends on the concentration gradient. In normal circumstances, the value of the flux in the diffusion of substances depends on the concentration gradient, but the diffusion coefficient is generally constant. In the case of the present invention, due to the metal-sensitive compounds as described above, the diffusion "constant" is not actually constant, but is itself dependent on the concentration gradient. Thus, within certain limits, if it is desired to operate an electrochromic device more rapidly, it is necessary to make the metal-sensitive membrane even thicker rather than thinner.

Thus, the present invention improves the "writing" of electrochromic devices by determining the optimal thickness of the metal-sensitive compound layer while taking into account the other factors mentioned above, such as the average particle size and stoichiometry of the material.
Provide a baseline for reducing time.

Considering in more detail the relationship between particle size and manufacturing technology, it is clear that when a layer of metal-sensitive material is deposited, for example by evaporation, the faster the evaporation rate, the smaller the particle size. It is publicly known. According to the present invention, the material should evaporate quickly to obtain a small particle size, but within certain constraints. One constraint is that evaporation must not be so fast that the material becomes non-stoichiometric, which is visible in the color of the material.

Considering the example of tungsten trioxide, if the substance is pure and stoichiometric, the formula can be written as _WO3 . If _{the substance is not stoichiometric, the formula is written as WO 2.9 ,} for example. This indicates that in such cases the ratio of oxygen to tungsten is not the normal amount required by standard chemical formulas as required by simple theory of valence. This occurs, for example, if a premature evaporation technique is attempted. When heating the tungsten trioxide raw material, if it is heated too vigorously, some oxygen will escape and produce non-stoichiometric _WO3 . Thus, some oxygen is lost out of the system through the vacuum pump, so that when evaporation begins, excess tungsten is deposited because some oxygen has been lost in the vacuum system. In fact, this gives the normal WO ₃ crystal structure, but some oxygen atoms are missing from the structure. This effect thus places a constraint on the rate and limit at which tungsten trioxide can be evaporated when attempting to obtain small particles.

In practice, this is recognized by the fact that during evaporation the oxygen pressure in the gas system can be checked. Evaporation is adjusted to occur at the beginning of the evaporation cycle when oxygen pressure is rising. The evaporation process ends when the oxygen peaks and begins to fall. If more deposition is required, fresh feed is provided and the evaporation cycle begins again. Typical evaporation rate is 30Å per second
It is. This typically yields an average particle size of 50 Å. The term average particle size means the reciprocal of the number of particles in a unit length. For example, the average particle size is actually determined by taking an enlarged photo of a substance using an electron microscope and drawing a straight line across a group of randomly selected particles.
It is measured by counting the number of particles crossed by a straight line along a chosen unit length. One concept of the idea of average particle size is that if the particles were all spherical and placed side by side along a straight line, the average particle size would correspond to the diameter of the spherical particles. . The particles are observed using a high energy electron microscope, such as a 1 million volt electron microscope.

Typically, when depositing by evaporation, a sample is taken and placed in a silica glass tube with a resistance heater around its periphery to raise its temperature, increasing the vapor pressure and vaporizing the material. This is done in a vacuum system and the material is deposited on a cold surface.

If the rate of evaporation or sputtering is too fast,
The deposited material will be stoichiometric in the first deposited layer, but will no longer be stoichiometric for the required thickness. This factor was not as important in prior art systems as it was desired to keep the film as thin as possible, but according to the present invention (to reduce the diffusion time in the intentional color development of metal-sensitive substances) (As the importance of relatively thick films is recognized in It has been found that it is important to maintain

Thus, to summarize the importance of evaporation rate, it is desirable that evaporation be rapid to obtain small particle sizes, but non-stoichiometric layers (which can result in undesirable coloration of metal-sensitive materials) may be It is desirable not to evaporate too quickly to produce the relatively thick layers required.

It will be appreciated that other techniques alternative to those described above are available to those skilled in the art for the manufacture of the various components of the device of the invention. Such techniques include sputtering (including reactive sputtering involving simultaneous chemical reactions, such as the sputtering of tungsten in oxygen), chemical vapor deposition from unstable compounds, and chemical precipitation, as well as the evaporation methods mentioned above. be done. The choice of manufacturing technique to be used will be based on the chemical nature of the components to be produced and the required physical form.

〔Example〕

Embodiments of the invention will now be described by way of example with reference to the accompanying drawings, in which: FIG.

In FIG. 1, a device generally designated 11 is enclosed in a transparent box 12 of, for example, synthetic resin material.
The active layer of device 11 is encapsulated in silicon oxide, represented by outer layers 13 and 14. The viewing plane of the device is the upper side of FIG. 1, and looking at the layers of the device from top to bottom, the first layer below the encapsulation layer 13 is the indium-tin oxide layer 15 which constitutes the first electrode. Below this is a layer 16 of color-responsive metal-sensitive compound.
The material shown in this example is tungsten trioxide. Next underneath is a layer 17 of fast ion conductor, shown in this example as lithium-β
- alumina, which in its preferred form has the formula Li
−β-alumina. Then, below this is a layer 1 of tungsten trioxide containing lithium atoms.
8, this layer constitutes the second electrode, which in the preferred form is Li _x WO ₃ (x is preferably 2).
It is expressed as The indium-tin oxide top layer 15 has a metal contact 19, and the second electrode 18 is connected to a second contact 20, which is shown projecting from the casing 12, which contacts the section shown in FIG. It is connected to layer 18 on the outside of.

FIG. 2 schematically depicts a series of steps in one preferred method of fabricating a device, generally as shown in FIG. 1, in accordance with the present invention. The method of attaching the first electrode described with reference to FIG. 2 does not necessarily correspond to the cross section shown in FIG. 1, but the relationship between FIG. 1 and FIG. 2 is generally similar and similar. Similar reference numbers are used for elements.
However, the contact 19 is indium oxide-tin layer 1
The special method of attachment to 5 will produce a slightly different result from that shown in FIG. 1 and will be explained in detail in FIG.

In FIG. 2a, the device is constructed, for fabrication purposes, on a ceramic fast ion conductor 17 which constitutes the base body. First, a ceramic substrate 17 has a highly polished surface and a water-free polycrystalline oxide bronze film 16 is deposited on a dry β-alumina.
Deposited through a mask giving the seven compartment pattern shown in Figure a. Next, as shown in FIG. 2b, the indium-tin oxide layer 15 is formed precisely on the tungsten trioxide layer 16 by a masking method so that it does not come into contact with either the indium-tin oxide layer 15 or the alumina layer 17, as shown in FIG. It is attached with care.

Next, a layer 13 of silicon dioxide is shown in FIG. 2c.
A is on the side of the device, and the right hand side of the device is unmasked and placed over the silicon dioxide 13A in a position such that it forms a "stand-off" overlapping the edges of layers 15 and 16. The two contacts 19A and 19B then contact the left-hand segment of the indium-tin oxide layer 15 on the silicon dioxide standoff layer 13A, as shown in FIG. It is deposited without contacting layer 17.

Next, lithium was added to the back of the alumina substrate 17.
A layer 18 of tungsten bronze and indium-tin oxide 15 containing in the proportions indicated by Li ₀ . ₂ WO ₃
A conductive coating such as chromium metal (or about 0.1 micron thick chrome metal) is applied, followed by the application of an encapsulant layer to the entire bottom of the device 14, as shown in Figure 2h. These last two layers are not shown in detail in FIG.

Various practical details that must be considered in constructing the preferred device according to the invention will now be described.

In the illustrated examples, the substrate 17 is the mechanical support for the display and provides the background "color", which color is preferably white. A typical base material is Li ₂ O called Li-β-alumina:
8Al ₂ O ₃ , lithium sodium β-alumina, Na
-β-Alumina is LiNaO: 8Al ₂ O ₃ and “Nasicon” Na ₃ Zr ₂ PSi ₂ O ₂ . All of these are white ceramic materials with a thickness of about 0.25 mm or more. If the thickness is less than this, it cannot be used because the electrodes at the back are visible from the front of the cell due to the transparency of the substrate. The substrate is preferably highly densified (typically 99.5%) and of small particle size, typically 2μ. The base body is highly polished to a roughness of less than 0.5μ on both the front and back surfaces. The surface is cleaned and dried at high temperature (200°C) in a drying gas or vacuum.

The "standoff" layer 13A is, for example, _MgF2 (vapor deposited) or _SiO2 (sputtered). Methods for depositing such thin transparent electrically insulating films are well known.

Contains no water, which is required as a metal-sensitive layer
Many methods are used to obtain _WO3 . The first method is to combine WO ₃ with large particles (e.g. 1/10 diameter
mm) is sintered near its melting temperature.

This large particulate material is evaporated to create a water-free deposit. Another possible film fabrication method is reactive sputtering of tungsten in O ₂ . Although the film thickness can be adjusted, the key average particle size factor is quite complex. As previously discussed, the smaller the average particle size, the faster the final velocity of the display element. An evaporation rate of several hundred Å/second gives an average particle size of about 50 Å. about
Sputtering at 10 Å/sec gives an average particle size of about 100 Å.

As already mentioned, a very important material parameter is the diffusion coefficient of the metal ion into the substrate material (and its temperature coefficient).

Examples of diffusion coefficients in limitingly low concentration gradients are: Na in WO ₃ at 25°C; 6×10 ⁻²⁰ cm ² /s Li in WO ₃ at 0°C; 5×10 ⁻¹⁷ cm ² /s Electrode A transparent induction coating to be formed 15
is 0.8In ₂ O ₃ /0.2SnO ₂ (referred to as ITO), which is deposited on WO ₃ at room temperature using direct current or radio frequency (RF)
It is sputtered to give a sheet resistance of approximately 100Ω/plane. It is important to maintain the sputtering speed and the pressure of the sputtering gas O ₂ /Ar at appropriate conditions in order to maintain high transparency of the conductive film. The importance of these conditions is well known to those skilled in the art. But about 200℃ is for example WO ₃
It must be remembered that this is the highest temperature that the membrane can reach without failure.

In operating the device that is an embodiment of the present invention, it is necessary to consider some circumstances of device operation. For atomic intercalation systems of the type described above, a charge of 1 to 8 millicoulombs/cm ² is typically required for color development of the cell. Not only is this range of charge necessary, but the substrate solid must be able to sustain this charge for a given period of time without deleterious side effects. The only significant deleterious effect was found to be electroplating the metal rather than dissolving it into the substrate. To prevent this, a certain limit should be placed on the amount of metal insertion. For example, when the metal-sensitive compound is represented by Li _x WO ₃ , x
is preferably not greater than 0.25. This improves the safety factor and ensures that no change in color density occurs after writing.

Applying a constant voltage, which is a more or less practical approach, provides a high current density at the beginning of the write pulse. This can cause difficulties and it has been proposed to increase the initial part of the write voltage pulse exponentially over about 1/10 of the total pulse width.

Another factor to be aware of is that if it is "over-bleached" it is detrimental to the functioning of the electrochromic display device. "Over-bleaching" occurs when a positive voltage is applied to the electrode for too long, and the resulting metal-free WO ₃ has a high resistance. this is
This can be prevented by incorporating a background body in which metal is permanently embedded in WO ₃ to provide a background conductor that prevents "over-bleaching". Thus adding aluminum metal into the _WO3 evaporation source dilutes Al _x
This results in the production of _WO3 . The total amount of Al is 5×
It should not exceed 10 ¹⁵ cm ^-2 and up to 5 x 10 ¹³ cm ^-2 , the preferred value being 1 x 10 ¹⁵ cm ^-2 .

Specific fabrication examples of devices embodying the invention are described next.

EXAMPLE 1 A 0.75 mm thick 2 inch by 2 inch section of lithium-β-alumina having a conductivity at room temperature of approximately 2000 ohm-cm is placed in a vacuum chamber. Lithium
β-alumina is represented by the formula Li-β-alumina. Tungsten oxide containing almost no water
The raw material of WO ₃ is heated to about 1350° C. by a resistance heater in a vacuum chamber using liquid N ₂ and kept in an anhydrous state by a cryo-pump.

Tungsten oxide is deposited through a mask onto the lithium sodium alumina for 3 minutes at a deposition rate of 30 Å/sec. The average particle size of the deposited tungsten trioxide is 50 Å and the thickness of the deposited layer is approximately 0.5 μ. The tungsten oxide source and the vacuum system in which the evaporation takes place are kept sufficiently anhydrous so that the deposited tungsten trioxide has less than 0.5 mole percent moisture. Oxygen pressure within the evaporation chamber is regulated during evaporation and evaporation is terminated before a significant drop in oxygen pressure is detected. The evaporation is carried out in such a way that the layer of tungsten trioxide deposited is kept stoichiometric to the extent that throughout its depth the loss of oxygen atoms from the deposited layer is less than 10 ¹⁵ per cm ² . Ru. Then on top of the tungsten bronze layer tin and indium oxides SnO ₂ and In ₂ O ₃
An indium-tin oxide electrode is deposited by sputtering from a target consisting of a compressed homogeneous mixture in an 88:12 ratio. The indium-tin oxide layer is optically transparent and has a thickness of approximately 0.75μ and a resistivity of 100 ohms/cm ² . Indium oxide
Take care to avoid direct contact of the tin with the alumina layer. This is accomplished by depositing a 0.15 micron thick "standoff" layer of silicon oxide in the manner generally described with reference to FIG. 2 above. The substrate is kept at room temperature throughout.

The back side of the lithium-beta-alumina substrate was fabricated with the formula Na ₀ by a two-source evaporation method in which both lithium oxide and tungsten trioxide were evaporated onto the substrate.
It is coated with a layer of tungsten bronze containing lithium atoms up to the limit expressed as ₂ WO ₃ . Indium-tin oxide electrode contacts are then deposited on the lithium tungsten bronze and the back side of the device is covered by an encapsulating layer of silicon oxide of about 0.2 microns.

Care must be taken to maintain the materials and operating conditions in an anhydrous state throughout the manufacturing process by commonly available techniques. It is also necessary to prevent the indium-tin oxide layer from coming into direct contact with the alumina substrate. For this reason, both sides of the substrate are highly polished prior to the deposition of tungsten bronze on their surfaces, since irregularities in their surfaces can result in indium-tin oxide contacts through the tungsten bronze. . Contact between the indium-tin oxide and the alumina substrate creates the possibility of lithium release at the interface, which can result in device failure.

An alternative embodiment of the electrochromic device shown in FIG. 1 will now be described with reference to FIG. 4a. The modification is that the layer of fast ion conductor is made transparent (instead of opaque in Figure 1) and the second electrode is made optically reflective, so that a mirror effect occurs when the second electrode is placed at the rear of the device and viewed. The reason lies in the fact that it was designed to give

In FIG. 4, device 111 is constructed by depositing appropriate layers on glass substrate 110 using techniques and materials generally similar to those described above. The glass substrate 110 is preferably 1 to 3 mm thick and the first layer deposited is
An indium-tin oxide layer 115 with dimensions and properties as described above is the first electrode of the device. In order to prevent contact at the edges between the layer of ITO 115 and the next layer of material, various standoff layers 113A of SiO ₂ are deposited by the method described above. The SiO ₂ layer 113A is preferably 0.1 to 0.5μ thick, most preferably 0.2μ thick.

Next, to form the amount of metal-sensitive compound, WO ₃ (MoO ₃
A layer 116 of (or mixed oxide) is deposited. Then a solid fast ionic conductor, e.g. Li ₃ N
A layer of fast ionic conductor is deposited. Preferably layer 117 has a thickness of 0.1 to 3.0μ, more preferably 0.2μ.
The thickness is between 1μ and 1μ, most preferably 0.5μ. An optically reflective layer 118 is then deposited which forms the second electrode and serves as a source and reservoir for metal ions to be inserted into the fast ion conductor 117. For example, optically reflective layer 118 may be aluminum containing 31/2 atomic percent dissolved Li. The layer is 0.3 to 3μ, preferably 0.5
The thickness is between 2μ and 2μ, most preferably 0.8μ.

Finally the device is coated with a background body layer 113. This layer is conveniently an encapsulation layer of SiO ₂ as explained above. Instead layer 113
can also be chromium metal with a thickness of 0.1 to 0.5μ, preferably 0.2 to 0.4μ, most preferably 0.25μ. Furthermore, the layer 113 may be Al ₂ O ₃ deposited on the outside of the aluminum electrode 118, where the Al ₂ O ₃ is produced by oxidation of aluminum and is a cohesive (non-porous) oxide film. be.

The operation of the apparatus shown in FIG. 4 is generally similar to that shown in FIG. 1, except for the mirror effect already mentioned. Various patterns, such as a 7-segment display, can be constructed using metal masks to delineate the contours, or photolithography techniques may be used, provided care is taken to avoid the use of water. The second (or counter) electrode 118 is a reflective surface and the solid electrolyte 117 is thin enough to absorb very little light (ie, less than 50% absorption, preferably less than 10%). The device is glass 11
observed through 0. In the non-written state, a mirror-like reflection is observed, and in the written state, the WO ₃ layer 116 into which metal atoms are inserted is blue, and a blue hue with depth according to the amount of inserted metal atoms is observed. be done.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an electrochromic device according to an embodiment of the invention; FIGS.
FIG. 3 is a cross-sectional view of a part of an electrochromic device according to the invention; FIG.
The final result of steps a to f is shown diagrammatically in the figure; FIG. 4 shows a modification of the electrochromic device of the invention in which one electrode is optically reflective to provide a mirror effect. FIG. FIG. 1 shows a cross-section of an electrochromic device according to the invention, except that FIG. 1 and the other figures are not drawn to scale and in particular the layer thicknesses may vary between the various layers. does not necessarily indicate the scale ratio.

Claims (1)

[Scope of Claims] 1 Consists of a first electrode and a layer of a metal-sensitive compound in contact with the first electrode and in contact with a solid fast ion conductor, wherein the fast ions in the fast ion conductor are dissolved in the metal-sensitive compound. The fast ion conductor itself has a second ion that can donate the same ions as the fast ions of the conductor.
In an electrochromic device in contact with an electrode, the metal-sensitive compound is (i) substantially stoichiometric; (ii) substantially free of water; (iii) in the range of 40 Å to 250 Å; and (iv) a layer thickness ranging from 0.2μ to 2μ. 2. A step of attaching a metal-sensitive compound to at least a part of one side of the base of the fast ion conductor, which contains metal ions as fast ions that change its color when dissolved in the metal-sensitive compound, the first electrode and the fast ion conductor. depositing a first electrode on at least a portion of the metal-sensitive compound to prevent direct contact with the fast ion conductor; the step of depositing a second electrode capable of donating the same ions (however, the order of the steps is not necessarily in the order listed), the step of depositing the metal-sensitive compound (i) rendering the deposited material stoichiometric; (ii) depositing the metal-sensitive compound from a substantially water-free compound source in a substantially water-free atmosphere; (iv) depositing a metal-sensitive compound in a layer having a thickness of 0.2μ to 2μ; 1. A method for manufacturing an electrochromic device, comprising the step of depositing at a speed and time sufficient to achieve the desired results.