DE2655209A1 - ELECTROCHROMIC DISPLAY DEVICE AND SUITABLE ELECTROCHROME MIXTURE - Google Patents

Description

IMPERIAL CHEMICAL INDUSTRIES LIMITED London, United Kingdom

Electrochromic display device and suitable therefor electrochromic mixture

The present invention "relates to electrochromic display devices, whose display results from an electrochemically induced color change on an electrode surface results as well as suitable electrochromic mixtures or substances.

The invention particularly relates to display devices with working and counter electrodes in contact with an electrolyte mixture.

Electrochromic systems are described in Applicant's British Patent No. 1,314,049

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(i.e. systems in which an electrochemical process on an electrode surface causes a change in appearance is brought about, wherein the electrochemical process results in a change in the color of the electrode or one Part of the same - usually as a result of material deposition or removal on or from the electrode surface - leads), in which an electrolyte mixture is in contact with working and counter electrodes and is carried out Energy supply to selected electrodes a display effect is achieved. Others for use in electrochromic! Mixtures and compositions suitable for e-display devices are described, for example, in US Pat No. 3 806 229 and the BRD Offenlegungsschriften 2,449,278, 2,511,314, and 2,527,638 are suggested.

When electrochromic systems, as described above, are used as display devices, the electrolyte mixture in contact with two electrodes or electrode systems of opposite polarity brought: With the working electrode, which is usually involved in the display, and the counter electrode, which is usually is arranged so that changes in its neighborhood or on its surface upon display do not become visible or do not appear strongly.

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One or more working electrodes are arranged relative to a background that has a first level of contrast compared to an electrode with material deposited thereon and a second contrast level compared to an electrode without any material deposited thereon. Usually the first contrast level is high and the second low, but it is clear that the background can also be chosen so that its appearance is less contrasting versus the deposited electrode shows than versus the deposition-free electrode.

If the display device has more than one working electrode and / or more than one counter electrode, some of the electrodes may be electrically connected to one another so that they are energized or turned off at the same time, effectively resulting in a single divided electrode. In the following - unless otherwise stated - both the working electrodes and the counter electrodes, regardless of whether they are provided individually or in a multiple arrangement, are referred to as "electrodes" and the electrodes involved in the display are, regardless of whether they are working or Counter electrodes or both, hereinafter referred to as "display electrodes ¹¹ ".

In such a device, at any particular point in time during a current flow through elec-

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trochemical effect at the same time a material deposition or color enhancement in the neighborhood or on the surface of an electrode of one polarity and a removal of deposited material or reduction the color intensity in the vicinity or from the surface of an electrode of the opposite polarity brought about.

It has now been found that it is sometimes advantageous if the electrolyte or the electrolyte mixture is translucent or is made opaque, and it has been found that it is particularly useful if the electrolyte mixture by introducing a finely divided inorganic material, depending on its suitability, makes it translucent or opaque, which has such a density or particle size that it remains distributed throughout the electrolyte mixture (either because of the given nature or as a result of this and an occasional movement such as a wristwatch) .

According to one aspect of the invention, an electrochromic A mixture is provided which comprises an electrolyte and an opacifying agent.

The invention also includes an electrochromic display device with a housing in which the working and counter elec-

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electrodes are included and an electrochromic mixture in contact with the electrodes, which is an electrolyte and an opacifying agent.

Preferably, the layer thickness of the electrochromic mixture in the range of 5 μ to 5000, in particular 10-1000 μ. The layer thickness is usually determined by the interior space or the depth of the housing.

Under an "electrochromic mixture" is meant one for the Use in an electrochromic display device of the type described understood useful composition.

A substance is referred to as an "opaque agent" which obstructs the passage of light and whose presence makes the electrochromic mixture containing them translucent or makes it opaque.

The degree of opacity of the electrochromic mixture to be chosen will depend on the intended application the electrochromic display device in which the mixture is to be applied. That is, if the Display electrodes are surrounded by the electrochromic mixture, it can of course not be opaque. if the display electrodes transparent or practically transparent and in contact with a transparent area or a are practically transparent area of the case, so may

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the electrochromic mixture be opaque and for example create a contrasting "background". Choosing an appropriate level of opacity for the electrochromic mixing in any particular application is usually determined by simple experimentation and therefore do not give up any difficulties to the person skilled in the art.

Although electrochromic mixtures according to the invention will usually be flowable, the possibility will be not using a solid or semi-solid mixture excluded, of course, the essential compositional requirements, i.e. adequate electrical Conductivity and ion mobility are taken into account.

It is also contemplated that the opacifying agent may be in the form of a polymer base material, preferably of a hydrophilic polymer, in which the electrolyte is distributed (at least over a substantial part of the same) can be; the resulting electrochromic mixture can then be practically solid.

Preferably the opacifying agent is particulate Material and in particular an inorganic particulate material. With such a mixture can the electrolyte (e.g., in a relatively small amount) is absorbed on the surface of the particles, so that the particles

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be arranged so that there is an electrical continuity for the electrochromic mixture, the substantially is solid or the particles can be distributed over a relatively large volume of a liquid electrolyte mixture so that a substantially non-solid electrochromic mixture results.

If an opaque, practically solid electrochromic mixture is required, the particle size is preferably 1 to 70 microns. If a translucent electrochromic mixture is required, the opacifying agent is preferably a finely divided inorganic material of such a density or particle size that it remains distributed throughout the electrolyte mixture. More preferred are materials with a particle size (the longest axis) of 5 to 100 nm. Particularly preferred are oxides of groups III and IV of the periodic table and in particular so-called pyrogenic oxides or mixtures of oxides of groups III and IV of the periodic table, such as silica or alumina.

"Pyrogenic oxides" are oxides or mixtures understood by oxides, which by a "flame hydrolysis technique" formed, which is usually a spraying of metal chlorides into an electric arc in the presence comprised of hydrogen and oxygen.

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The concentration of finely divided inorganic material in the mixture according to the invention can (correspondingly with the achievement of the properties selected as mentioned above) vary within wide limits. The concentration will depend on the degree of acceptable or desired firmness or flowability of the mixture, the nature of the inorganic material, the mean dimensions of its particles, etc. vary. The expert the determination of suitable concentrations on the basis of simple experiments will not present any difficulties. It has thus been found that the concentration of the finely divided inorganic material is usually within a range will be from 2 to 20% by weight, preferably 5 to 15% by weight, and especially about 10% by weight, although concentrations well outside these limits may be suitable; the appropriate concentration for any given combination of components can be determined by simple experimentation.

Although the finely divided inorganic material is preferably white or colorless, the possibility will be the use of a colored, finely divided inorganic material in a mixture according to the invention is not excluded. Such materials can be colored by themselves or using one with the finely divided one inorganic material and the intended environment

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wearable dye. In the application a colored, finely divided inorganic material is a necessity to achieve the desired contrast with the display electrodes.

If the opaque agent is through a finely divided inorganic material is formed, solid or semi-solid electrochromic mixtures, for example by Incorporation of a gelling agent in suitable concentration in the electrolyte mixture can be prepared, although It should be noted that the finely divided inorganic materials themselves act as gelling or solidifying agents can work; they can be used alone or in conjunction with another solidifying agent will. When using a gelling agent, an organic gelling agent such as polyacrylamide, Polyvinyl alcohol or guar gum are preferred. If preferred an inorganic gelling agent, the finely divided inorganic material is preferably fumed silica or fumed silica / alumina is formed.

Additives to the electrolyte mixture must of course - regardless of whether they are opacifying agents or gelling agents - Be chosen so that they do not adversely affect the operation of a display device in which the mixtures according to the invention are introduced; at-

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For example, they should not be used with any component of the device (including the electrolyte mixture) react in the way that proper operation is prevented and opacifying agents should be so low Solubility that their effectiveness as opacifying agents does not come from dissolution in the liquid Component is noticeably affected.

It has been found that the finely divided inorganic Materials according to the invention when used with some electro-chromic electrolyte mixtures, in particular with those as indicated in the patents mentioned will affect the rate of electrochromic response of the device; in particular was an acceleration of the fading was observed.

The working electrodes are viewed against a background which is a component of the device, for example an opaque or translucent support surface or an environment for the working electrodes. Alternatively, the device can be transparent so that the electrodes are viewed against an external background can be. This is particularly advantageous when using clear electrodes.

If the electrodes with the background or under- 709825/0688

Should be in great contact, this will of course be like that chosen so that the electrodes are effectively electrically isolated from one another. However, the subsoil has to be not necessarily be formed from electrically insulating material alone; it is only necessary that he is not electrically conductive to the extent that the local electrode effect is disturbed or eliminated.

W _e nn the opacifying agents by a particulate material formed to the electrochromic mixture most conveniently obtained simply by mixing the Opakisierungsmittels with the electrolyte mixture. The electrochromic mixture can then be suitably injected into a housing which includes the electrodes and the background.

The invention is based on the attached schematic representations of examples for a typical device described with mixtures according to the invention, in which the arrangements of the components vary.

Fig. 1 shows a typical display device in perspective with a housing 1 in which display electrodes 2 in a suitable manner Way for a digital display are arranged. The electrodes can of course be provided differently than shown

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or are arranged. The display electrodes are surrounded by a suitably located transparent area 3 of the housing visible. The cavity 4 of the housing contains the electrochromic mixture.

The device shown also includes a background (5)> opposite which the display electrodes are viewed and part of the housing wall can form or be inserted into this. The electrodes can be in contact with the background (Fig. 2) or they can form a distance to this (Fig. 3) or there can be some with the background in Being in contact and others can be at a distance, so that a spatial impression is created.

The electrodes are often preformed before being put in the housing to be installed; alternatively, they can be in situ on the background or other components of the Device can be formed, for example, by etching or a metal deposition process.

Fig. 4 shows a structure in which display electrodes are removed from the background, suitably on the inside a transparent wall of the housing are arranged.

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The term "background" or. ⁿ U _n ⁿ tergrund, as used herein, is not limited to a component that is necessarily arranged in a different plane relative to the electrodes or necessarily continuous. 5 shows a display device with display electrodes 10 and a back or a background 11 in the same plane, both of which are provided on a base 12. This special arrangement is particularly expedient because when the base is removed from the housing in such a way that the electrolyte can reach the back of the base, counter electrodes 13 can be arranged on the side of the base facing away from the display electrodes.

In another embodiment, the background itself can be an electrode that corresponds to the display electrodes can act as a counter electrode. This is illustrated by FIG. 6, which is a perspective Representation of a device with electrodes 14 and 15 shows.

In yet another embodiment, the electrodes can be arranged such that at least some or both of the working and counter electrodes are display electrodes. Examples of such display devices are in Figures 7, 8 and 9 reproduced.

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According to FIG. 7, the working electrodes 17 and the counter electrodes 18 are spaced apart from one another, but are arranged in such a way that that they are visible inside the housing. Reversing the polarity of the electrodes will result in that the working and counter electrodes alternately exhibit electrochromic effects, so that each set of electrodes may (but need not necessarily) show a different pattern. For example, in a watch, the Working electrodes show the time and the counter electrodes show the date.

Fig. 8 shows an apparatus in which the digital patterns are more closely spaced than in the previous apparatus are provided.

In Fig. 9, a double-sided display device is shown in which the working and counter electrodes are on opposite sides Sides of a (expediently opaque) background or carrier are arranged, wherein both are visible through the corresponding wall of the housing.

To improve the overview, connections to control means, the control means, are shown in FIGS itself and energy sources etc. omitted. Such control means can, for example, be timing devices

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(for displaying time, date, etc.) Temperature measuring devices Batteries are usually used as energy sources, but induction currents, solar energy and bio-electric energy not excluded.

The device according to the invention is particularly suitable for a multiplication, with information or control can be passed independently to one or more electrodes without necessarily requiring a There is separate access to each electrode. For example, it could be a nine-digit display of 9 digits, where each digit consists of 7 electrodes, the 9 x 7 = 63 separate leads and an anode lead would require when multiplexing by a total of 7 electrode leads and 9 anode selection lines (preselection lines), i.e. a total of only 16 connection lines can be controlled. The system is shown in FIG.

Leads (a) to (g) are leads to single display electrodes; the preselection or sorting lines become represented by I to IX. For example, to display the number 7 at the left end, the leads (a) would be (b) and (c) as well as to supply the sorting line I with energy (where (a), (b) and (c) with one pole and I with the connected to others). Correspondingly,

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"and to supply Vorwählleitung II with energy at a." wählung the second position the appropriate display electrode leads and the sorting preferred apparatus, each of the display electrodes "Ausbleich ¹¹ - and" deposition "controllers, each line a diode, for example, of silicon or Has germanium, so that current only flows if the voltage is "correctly" polarized and has a value above 0.2 V (for Ge) or 0.6 V (for Si).

It is clear that the degree of opacity when the display electrodes through the electrochromic mixture should be considered, such as in the case of the devices of FIGS. 2, 3 and 9, for example must be that the display is sufficiently visible through the mixture, i.e. completely opaque Mixtures would not be suitable. If the display electrodes are not viewed through the electrochromic mixture must be (see Fig. 4) an opaque mixture can be used and an acceptable one Form a background against which the electrodes can be viewed. The degree of opacity can be by changing the concentration and / or dimensions and / or nature of the particulate material in the electrochromic mixture can be changed.

The invention is explained below using examples. 709825/0688

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example 1

A display unit was constructed on an aluminum oxide support of 25 10 χ 0.5 mm as follows:

A coating composition for a uniform white glaze (79 T5 in the medium 65/101 from Blythe Colors, Stoke-on-Trent) was applied by screen printing in 10 μ thickness on the alumina carrier and 30 minutes baked at 950 ⁰ C for.

A digital display-electrode assembly, the leads and pads were applied and fired at 850 ⁰ C under obtaining a layer thickness of the component is between 0.1 then through an appropriately patterned mask by screen printing on the glaze using "Gold 9425 resinate" (from Engelhard) and 0.5 / rev.

Thereafter, a coating for a dielectric glaze by screen printing to cover the entire support was on the digital display electrodes and contact pads applied and fired at 75O ⁰ C (in 63/2 solvent from Blythe Colors 11 H34 glaze).

Then a gold counter electrode (background) was applied by screen printing over the dielectric glaze, taking care not to interfere with the digital

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display electrodes or contact points came into contact (gold resinate as above) and baked at 65O ⁰ C.

The device was completed by a the counter electrode area, but not the contact points encloses alumina ring close to the support to form the housing was applied, which was closed with a glass lid by printing "solder glass" and baking at 500 ⁰ C densely ⁿ welded The cavity of the housing was filled with the following electrochromic mixture through an opening in the ring, which was then sealed:

An aqueous electrolyte solution (EC) with the following composition:

Ferroammonium sulfate 0.5 M.

D ⁺ - ¥ one acid 0.25 M

N, N '~ di- (p-cyanophenyl) - _{nm M} 4,4'-dipyridyl sulfate (CPPS) ^υ » ^{υΊ η}

was made under nitrogen using distilled deionized water. Fumed silica ₅ "Cab-0-sil", quality EH5 (7 nm), was degassed with a water pump for 8 hours and discharged under nitrogen.

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0.6 g of the silica was poured into one with nitrogen

brought flushed flask with paddle stirrer. 9.0 g of the EC solution were slowly added, with the mixture was stirred vigorously. The electrochromic mixture was obtained as a translucent pale green gel. The electrodes were due to the electrochromic mixture with passage of current with a change from gold to a dark green Appearance visible.

The cell was operated at 1.4 Hz at 1 V for 3 weeks.

Example 2

A display device was made from two parallel pieces of electrically conductive glass passing through a silicone rubber ring 4.5 mm thick were separated from each other. The inside of a piece of glass was wearing a screen-printed dielectric glaze in the form of a symbol. Activation of the symbol electrodes was done simply through the conductive glass.

An electrolyte mixture was prepared as in Example 1.

24 g of the electrolyte solution were slowly added with stirring 709825/0688

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added to the mixture to 11.4 grams of "ALON" alumina. A dark green color appeared immediately when the Electrolyte mixture and the "ALON" were brought together. Thorough mixing of the electrolyte with the "ALON" resulted in a dark green paste which was incorporated into the display device.

The display device was connected to an operating circuit and subjected to cycles of 0.5 Hz at 0.9 V; the areas of the paste in contact with the electrodes were alternately bleached and discolored. When the display device was removed from the operating circuit, it was bleached or lightened Paste does not turn green again within a few minutes.

When a sample of the paste was left to stand in the air for a few days, the color of the paste changed from green to fawn. The fawn material was alternately colored and faded when it was between two conductive ones Glass electrodes was exposed to an alternating voltage.

Example 3

An electrolyte mixture was made by dissolving N, N ^! ~ Di- (p-cyanophenyl) -4.4 ^l -dipyridyl sulfate

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(0.075 g), ferroammonium sulfate (3.92 g) and D (+) - tartaric acid in warm water (10 ml; distilled under Ν «). 10 ml of a silica solution ("Nafloc N1050 ⁿ ; 16-20 nm) was added to the electrolyte mixture.
Immediate coagulation occurred with formation
of a pale yellow gel. When this gel was used in the display device of Example 2, an electrochromic effect could be observed.

Example 4

Fumed silica ("Cab-0-sil" EH5) was used for
Removal of absorptions by pumped down for 3 days at 10 "Torr (τ). The silica was then drained and stored under Np.

An electrolyte mixture was prepared as in Example 1. 4.5 g of the fumed silica was placed in a flask with a high speed stirrer and an N ₂ inlet. The electrolyte mixture was slowly added with stirring. After the addition, stirring was continued for 5 hours. A pale yellow gel was obtained. When this gel was used in the display device of Example 2, an electrochromic effect was observed.

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Example 5

"Gasil ^w 23 / DK _silica (3 / µm) was degassed for 3 days at 10 torr.

An electrolyte mixture prepared as in Example 1 was slowly added to the silica with stirring. The stirring was continued for 3 hours. A white, smooth paste with about 20 % silica was obtained. When this paste was used in the display device of Example 2, an electrochromic effect was observed.

Example 6

Titanium dioxide powder (15 to 40 nm) was degassed at 10 torr for 3 days. An electrolyte mixture prepared as in Example 1 was added to the titanium dioxide under N £. The mixture containing 33% titanium dioxide was stirred vigorously for 3 hours after which a smooth, white paste was obtained.

Some of the paste was in the electrochromic cell given. When a voltage was applied, an image with a very good image contrast was observed.

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Example 7

An electrochromic mixture was prepared as in Example 6 using germanium dioxide (5 / im) as an additive made in place of titanium dioxide. A white cream was obtained which had a well-contrasting image could deliver.

Example 8

An electrochromic mixture was prepared as in Example 6, but using zirconium dioxide (5 / im) as the Additive made in place of titanium dioxide. A white paste was obtained which was capable of being a good one to provide contrasting image.

Example 9

An electrochromic mixture was prepared as in Example 6, but using talc in place of titanium dioxide. A pale green paste was obtained. When this paste is used in the display device of Example 2 was applied, an electrochromic effect could be observed.

Example 10

An electrochromic mixture was made as in Example 6 709825/0688

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produced, but using "Aerosil COK 84" (20 nm) in 12% concentration instead of titanium dioxide. The electrochromic mixture obtained was stiff, yellow in color and translucent. When the electrochromic Mixture was placed in a display device according to Example 2, non-colored electrodes were against the Gel background dark. Colored electrodes were visible through and against the mixture.

Example 11

An electrochromic mixture was prepared as in Example 6 using "Aerosil" type C aluminum oxide (5-20 nm) in place of titanium dioxide, the "Aerosil ¹¹ making up about 20% by weight of the mixture. The mixture was green / white Color and was almost opaque A display device as in Example 2 was filled with the mixture and an image with good contrast was obtained when the device was operated.

Example 12

An electrolyte mixture prepared as in Example 1 was added to degassed "Davison 952" silica, until the silica was slightly moistened. The silica

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kept their white color. A sample of the wet silica was placed in a display device according to Example 2 brought and compacted so that good electrical contact with the sides of the device and within the Silica mass was achieved.

When current was applied to the device, the silica surface adjacent to the glass cathode changed Colour.

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Claims (12)

Claims 1. Electrochromic display device with a housing and working and counter electrodes arranged therein, which are in contact with one another via an electrochromic mixture are, characterized in that the electrochromic mixture is an electrolyte mixture and an opacifying agent. 2. Device according to claim 1, characterized in that that the layer thickness of the electrochromic mixture is 5 to 5,000 ^ m. 3. Electrochromic mixture with a current passage to produce a color change on the surface of a electrolyte mixture capable of being in contact with the electrode, characterized by a content of an opacifying agent. 4. Electrochromic mixture according to claim 1, characterized in that that the opacifying agent is in the form of a polymer base material. 5. Electrochromic mixture according to claim 3, characterized in that that the opacifying agent is a particulate 709825/0688 shaped material, in particular a particulate is inorganic material. 6. Electrochromic mixture according to claim 5 »characterized in that that the particle size is 1 to 70 µm. 7. Electrochromic mixture according to claim 5 _f, characterized in that the particle size is 5 to 100 nm. 8. Electrochromic mixture according to claim 7, characterized in that that the particulate material by a pyrogenic oxide, in particular by fumed silica is formed. 9. Electrochromic mixture according to claim 7 or 8, characterized in that the concentration of the particulate Material between 2 and 20 wt.% Is. 10. Electrochromic mixture according to one of claims 5 to 9 »characterized in that the particulate Material is white or colorless. 11. Electrochromic mixture according to one of claims 5 to 10, characterized by an organic gelling agent. 12. The device according to claim 1 or 2, characterized by an electrochromic mixture according to one of claims 3 to 709825/0688