JP3041822B2 - Electrochromic device and method of use - Google Patents

Description

The present invention relates to an electrochromic device and a method for using the same. In particular, the present invention relates to an electrochromic transparent glass system, and more specifically, to a glass system in which light transmittance is adjusted by applying a potential to a glass terminal.
The glass of the present invention is used to control the brightness of sunlight inside buildings or automobiles, especially vehicles with glass roofs.

European published patent application EP-A-253713 and European patent application
According to EP-89 400814, a cathodic electrochromic material such as tungsten oxide (WO ₃ ), a proton conducting electrolyte such as polyelectrolyte, is sandwiched between two glass plates coated with a transparent electron-conducting layer, for example a tin-doped indium oxide layer. There is known an electrochromic glass system in which a copolymerization complex of ethylene oxide (POE) and orthophosphoric acid and an anodic electrochromic material such as iridium oxide are sequentially arranged. The two glass plates in contact with the electrolyte can reversibly introduce protons by applying an appropriate voltage to opposite ends of the glass system, and the introduction reaction into the tungsten oxide layer is based on protons from the iridium oxide layer. The iridium oxide layer acts as a counter electrode for the tungsten oxide layer because it corresponds to the removal reaction of the tungsten oxide layer. The thermodynamic equilibrium can be described as:

_{^{WO 3 + xH + + xe -}} <---> HxWO 3 and ^{HxIrOy <---> IrOy + xH +} + xe - instantaneous measurement of intensity I of the current across the glass layer, the introduction and removal reactions of protons occurs at the moment It is to measure the number of points directly.

The potential difference to be applied needs to be larger in absolute value than the thermodynamic potential difference of the proton introduction or removal reaction. The larger the applied potential difference, the faster the color development or decoloration is performed. However, when the voltage exceeds a predetermined voltage, a side reaction may occur to reduce protons to hydrogen molecules, or water remaining in any layer may be oxidized to oxygen.

Considering the overvoltage interface limits characteristic electrochemical stability of the system, the removal of a proton from the introduction and HxIrOy of protons in color phase i.e. WO _3, 0.
6 to 1.5 V, and -0.6 to 0 V in the decoloring phase. Hereinafter, these limit ranges are referred to as “electrochemically stable regions of color development and decolorization reactions”.

Further, as a second problem, there is a time required for performing desired coloring or decoloring. This means that, assuming maximum color development and decolorization, the time required to pass the electrical load corresponding to all reaction potential points, in other words, the current intensity I decreases to zero, or at least to zero. The time required to decrease to a near value.

As the size of the cell increases, the amount of electrical load passed increases correspondingly. However, the current intensity cannot increase proportionally. It can be said that R represents the resistance of the current conductor, which can be imitated to a good approximation with the resistance of the transparent conductor layer, so that the theoretical relationship between the potential difference V and the current I gives This is because it becomes smaller than V / R. For small size cells, the RI is very small and the RI increases rapidly as the cell size increases, and the voltage drop due to the ohmic resistance is a factor that limits the current and thus the rate of color development and decolorization.

In a light-transmitting cell, a material having a square resistance (plane resistance; the same applies hereinafter) of, for example, less than 1 ohm cannot be selected as a transparent conductor layer. Most currently used materials and deposition techniques can only achieve layers with a square resistance of 2-5 ohms. However, a current introducer composed of non-point strip or linear conductors extending along opposite sides of the cell and masked with a string forming a frame around the glass system to prevent leakage Can be used to partially exceed this limit. The strip-shaped or linear conductor can be selected from a good conductor such as copper, in which all points of the same strip have the same potential. As a result, when a glass-based surface is placed on an imaginary coaxial system xy whose horizontal axis x is parallel to the band of the current introducing body, all points having the same y become equipotential. On the other hand, two points having the same horizontal axis x and different vertical axes have different potentials unless the distance from the central axis, which is the axis of symmetry of the cell, is equal. Indeed, if the distance between the two strip conductors exceeds, for example, 10 cm, the switching time of the cell will exceed 1 minute.

Of course, this distance can be subdivided by increasing the number of conductive strips. Assuming that one conductive strip is located at y = 0 and the second strip is positioned at y = 1, as in the case of the glass system having a width of l, y = 1/3 ・ l and y = 2 Add a strip to / 3 · l, changing the contact surface. The cell thus formed is equivalent to an assembly of the same three small cells placed in parallel, each having a one-third lower resistance. However, when combined in this way,
The conductive band becomes a net-like shape, which impairs the appearance of the entire glass system.

Electrochromic glass systems do have a light-transmitting effect, but for example mirrors or other electro-optical devices of the display type, which necessarily have at least one transparent conductor layer which is relatively less conductive than a dense metal layer. Chromic systems also have optical transparency.

In addition, regardless of the mode of operation of the electrochromic system, ie, the introduction of protons or other cations, or the reduction / melting of, for example, metal salts, one will find similar problems based on voltage drops due to ohmic resistance. Would.

The present invention has a large area in which the time for repeatedly switching from the colored state to the decolored state is shorter than 30 seconds even if the width of the glass system is about 50 cm corresponding to the size of the glass window of a building or an automobile, for example. For electrochromic systems.

The technical problem is that two glass plates (1, 4) each covered with a conductor layer (2, 5) consist of an electrochromic material layer (9), an electrolyte (8), and a counter electrode (7). ), And the conductive layer (2, 5) has conductive strips (3, 6) made of a material having a higher conductivity than that of the conductive layer (2, 5). (3,6) are arranged along opposite sides of the glass system, and the power supply connected to these strips (3,6) is placed in the immediate vicinity of the strips (3,6). , 5) belong to two points A and B
And the potential difference U ₁ = (V _A
−V _B ) (t), whereby a potential difference between the point A and the point R, which is in a conductor layer different from the conductor layer having the point A and directly faces the point A, is applied. U ₂ = (V _A -V _R ) (t)
= U ₀ , wherein the electrochromic system of the present invention is configured to be a constant potential difference selected such that U ₀ is in the stable region of the chromogenic or decolorizing reaction.

The voltage drop due to the ohmic resistance is directly related to the distance between the electrodes and generally works with a conductive strip parallel to the length of the glass system.

As in the conventional method, a potential difference is applied between the two strips A and B, in other words between the two points at the ends of the ordinate axis, but by means of the present invention, a different conductivity is applied on the same side of the glass system. A potential difference is applied between two points having the same abscissa axis arranged on the body layer. According to this method, the effective voltage is maximum at time t = 0, from which fact the observer perceives color development or decoloration more quickly. It should be noted that the proposed voltage application cannot actually compensate for the voltage drop due to the ohmic resistance. When the voltage difference U ₀ is applied from one side of the glass system in this manner, the potential difference V (y) between two facing points except for the end of the glass system (y = 0 or y = 1) is obtained. , Always lower than the applied voltage. However, according to the results confirmed experimentally, this value V (y)
Is always higher than the value V ′ (y) obtained when V ₀ is applied between the two strips at the end of the glass system where U ₁ = U ₀ . As a result, the maximum color development is obtained very quickly, for example 40 × 80
The total response time can be about 30 seconds for a cm ² glass system.

Compared to conventionally known electrochromic glass systems,
The glass system of the present invention has a very noticeable difference between the transitional color development in the peripheral region and the transitional coloration in the central region of the glass system. The value of the effective potential difference between two facing points of the glass system is highly dependent on the location of these points, as described above. However, whatever the location, the effective potential difference is much higher than prior art glass systems. As a result, the color development is somewhat uneven, but the contrast is extremely strong. The edge of the glass system turns blue-black very quickly, but the color in the center does not appear until the end of the switching time. However, of course, from this moment, the color of the glass system becomes completely uniform.

According to the first embodiment of the present invention, a potential difference U ₁ to be applied at time t is obtained in order to obtain a constant potential difference U ₂ during the passage of time.
Is determined in advance by a voltage / current measurement recording device. Once these values are determined, the power supply can be designed accordingly.

To simplify this design, the curve U ₁ = f (t) can be approximately exponential. This simplifies the electronic components connected to the voltage generator, but does not require tests to determine the true size of each glass model in order to determine the parameters of the exponential function. is not.

In order to eliminate this difficulty in advance, it is preferable to use an assemblage with three electrodes in the form of a potentiostat, for example a practical amplifier. To do so, a reference electrode is placed at point R.
The problem with balancing the electrical load is that if the position of this reference electrode is on the straight line y = 0, then all points on this straight line are equipotential. Therefore, the reference electrode may be a conductive strip covering all or a part of the length of the glass system. In fact, the reference electrode may be configured in the same manner as the strip forming the electrode A.

When the reference electrode R is formed of a conductive strip having a glass length, it is preferable to mount the electrodes on two parallel sides of one of the two glass plates. This assembly has other disadvantages of electrochromic glass system,
That is, it is possible to improve that the reactivity is extremely low at a low temperature, particularly below 10 ° C. In this case, when a potential difference is applied between the two electrodes, the transparent conductive layer located between the two electrodes can be used as a heating layer by releasing heat generated by the resistance.

The potential difference applied for this preheating exceeds 20 V and is preferably about 24 V, and this value is generally 0.5
It corresponds to a voltage gradient of about V. This preheating phase precedes, for example, all color development and lasts about 2 minutes. Taking into account the vicinity of the second glass plate, this color hue tends to become blue with time, but this can be avoided by using an alternating current.

Other advantageous features of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings.

FIG. 1 is a principle view of the electrochromic cell of the present invention, and FIG. 2 is a sectional view of a glass roof of an automobile.

FIG. 1 illustrates an electrochromic cell. For simplicity, the ratios of the thicknesses of the various members of the system are varied in the figures. The configuration of this cell is as follows. The glass plate 1 is covered with a transparent conductor layer 2 and has a current introducing strip 3.
Having. This strip 3 is preferably parallel to the direction of the length L of the glass system. The width of the glass system is l.
The glass plate 1 faces the second glass plate 4, which is likewise covered with a transparent conductor layer 5 and has a current-introducing strip 6. Two transparent conductor layers 2 and 5
In between, an anodic electrochromic material layer 7 preferably made of iridium oxide, a proton conductive electrolyte layer 8 preferably made of a polymer composite of polyethylene oxide and strictly anhydrous orthophosphoric acid, and tungsten trioxide And a preferred cathodic electrochromic material layer 9.

For purposes of illustration, a layer having limited properties is used as follows.

Substrate (1,4): Float glass plate with a thickness of 3 mm Transparent conductor layer (2,5): Tin-doped indium oxide layer deposited by magnetron cathode sputtering, thickness 400 nm Square resistance 5 ohm Cathodic electrochromic layer (9) A tungsten oxide layer deposited by vapor deposition of molybdenum in a vacuum of 5 × 10 ⁻⁵ Torr, thickness 260 nm. Electrolyte (organic polymer 8): a method for producing a solid solution of phosphoric anhydride in polyethylene oxide. In this state, 17.5 g of pure phosphoric acid and polyethylene oxide having a weight average molecular weight of 5,000,000 were dissolved in the solvent 1. Density 1.21, glass transition temperature -40 ° C, ratio of the number of oxygen atoms of polymer to the number of hydrogen atoms of acid O / H 0.66.

The common solvent was, for example, a 50:50 mixture of acetonitrile and tetrahydrofuran.

The solution was run down onto a glass plate coated with a tungsten oxide layer deposited as described above.

The thickness was made uniform by the doctor blade method.

The flow of the solution is performed in a humidity-controlled atmosphere, and the solvent is vaporized to a thickness of 50 μm, conductivity of 20 ° C. and 9.10 ⁻⁵ ohm.
^A film exceeding ^-1 cm ^-1 and light transmittance of 85% was obtained. The falling humidity is preferably 40 to 100 ppm, which optimizes the contrast obtained later.

Anodic electrochromic layer: An iridium oxide layer deposited by cathodic sputtering with an oxygen / hydrogen (80:20) gas mixture of 6 mTorr and a magnetic field applied, 55 nm thick.

The electrolyte layer is preferably deposited on the tungsten oxide layer immediately after depositing this layer. The glass-based assembly is pressurized to 15 kg / cm ² in an autoclave and heated to 90 ° C.

The above glass systems are exemplary and should not be considered as limiting the invention. The invention is applicable to all larger electrochromic cells.

By a conventional method, a point A, which can be considered as a point of the conductive strip 3, and a point B, which can be considered as a point of the conductive strip 6, are in a stable region of a desired electrochemical reaction. applying a potential difference V ₁ which is fixed chosen. Such an assembly was used for _three similar cells S ₁ , S ₂ and S ₃ . In these cells, the spacing between the current-introducing strips was 3,4.5 and 9 cm, respectively.

FIG. 3 shows a situation in which the coloring current intensity changes over time. For the two smaller cells, the current I _{0 at} t = 0 was proportional to the surface, and the color development times were nearly identical. After another 5 seconds, the substantial process of color development was completed. On the other hand, in the cell 3, the current I ₀ is not proportional to the surface and is limited by the voltage drop due to the ohmic resistance. In fact, this cannot be achieved for cells with a spacing of the current-introducing strips larger than 10 cm, unless a switching time longer than 1 minute is accepted.

Other methods of analyzing the problem, coordinates illustrated in Figure 1 (x, y, z) in (x, y, a) and (x, y, b) 2 single point is M _A and M _B To consider. In between these two points, the potential difference at time t is V = VM _A -VM _B. However, if one chooses conductive strips 3,6 of copper or any other good conductor, all points M on a given ordinate axis y
Can be considered as _A or M _B are each electrically potential. In Figure 4, curve 10 represents the change in the value of V the interval combination of the point M _A and M _B as a function of the longitudinal axis y. The cell interval is 14cm in points A and B, the potential difference U ₁ 1.4V is applied, it effective voltage V in the case of t = 0 is very lower than U _1, and the center of the difference between these voltages cells Indicates that it is significant in the region.

According to the invention, a fixed potential difference U ₂ is maintained between the point R on the conductive strip 6 ′ and the point A facing it, U ₂ =
Curve 11 is obtained at 1.4V. The combination of all points M _A and M _B, it should be noted that the potential difference V to be observed is always U ₂ below. For a given electrochemical reaction, it is possible and necessary to apply the value U ₂ of the potential difference in the electrochemical stability region sufficient conditions of the present invention. Other, except for the top side, the effective voltage is not equal to the applied voltage U _2. The present invention cannot eliminate all voltage drops due to ohmic resistance. But the comparison between curves 10 and 11, effective voltage curve 11 of the present invention, in all combinations of the point M _A and M _B, indicating that about three times of the curve 10. As a result, coloring or decoloring is extremely fast. In addition, the edge effect is more pronounced than the prior art combination, demonstrating that the current is transmitted almost instantaneously near the edge of the glass system, but slower in the central region. It is a feature of the present invention that color development proceeds from the edge.

For terminals A and B with a spacing of 14 cm, the color development time gain is 6 seconds, which is a 30% time gain. The gain is further increased for terminals at wider intervals. Thus, the short side of the electrochromic ceiling can be longer than 30 cm and the switching time can be less than 1 minute at 20 ° C. In this case, dividing the switching time by 6 can typically reduce from 3 minutes to 30 seconds.

In the aggregate according to the present invention, two current introducing strips 6 and 6 ′ are provided on the conductive layer 5. The electrical resistance of the conductor layer 5 can be used for heating the cell. Before coloring,
Between the points B and R, by applying a potential difference U ₃ for example 24V,
This increases the temperature of the electrolyte layer. This temperature is 20 ~
Maximum performance at 80 ° C. Potential U ₃ as AC, avoiding the polarization of the electrochromic material layer is preferred, and the case effective voltage for example 24V.
However, it should be noted that heating can be used regardless of the oxidation state of the electrochromic material layer.

As described above, the present invention has been described with reference to a cell having a proton conductive electrolyte.
It should be understood that all electrochromic systems can be applied, especially for cells containing an ionic conductive electrolyte such as lithium. Similarly, the electrochromic layer and the counter electrode can be realized using other materials such as those mentioned above, especially for the purpose of obtaining other colors, and by adjusting the value of the pre-applied voltage, Thermodynamic equilibrium can be exerted. Furthermore, an assembly with three electrodes, at least a transparent conductor layer, can be operated by any system that requires the introduction and removal of ions called in a memory, an electrochromic gel system, or a liquid crystal display. Can be widely used in systems.

[Brief description of the drawings]

FIG. 1 is a perspective view showing the principle of the electrochromic cell of the present invention, FIG. 2 is a sectional view of a glass ceiling of an automobile, and FIG. FIG. 4 is a graph showing the relationship between the interval (coordinate axis y) of the combination of the points M _A and M _B and the effective voltage. 1,4 ... glass plate, 2,5 ... conductive layer, 3,6 ... conductive strip, 7 ... counter electrode, 8 ... electrolyte, 9 ... electrochromic material, 10 ... conventional technology Cell, 11 ... cell of the present invention.

Continuation of the front page (56) References JP-A-63-305326 (JP, A) JP-A-2-75627 (JP, U) US Patent 4,927,246 (US, A) US Patent 4,902,110 (US, A) US Patent 4,865,428 (US, A) U.S. Pat. No. 4,845,591 (US, A) U.S. Pat. No. 4,842,221 (US, A) U.S. Pat. No. 4,807,977 (US, A) U.S. Pat. 3016309 (DE, A1) EP 338876 (EP, A1) EP 304198 (EP, A1) EP 253713 (EP, A1) EP 189601 (EP, A1) (58) Field surveyed (Int.Cl. ⁷ , DB name) G02F 1/15-1/25 G09F 9/30 380-388 G09G 3/19 G09G 3/38

Claims (14)

(57) [Claims] 2. The method according to claim 1, wherein the first and second conductor layers are respectively covered with conductor layers.
The transparent substrates (1,4) are separated by an electrochromic material layer (9), an electrolyte (8) and a counter electrode (7), and the conductor layers (2,5) are Conductive strip made of a material with higher conductivity than its conductive property (3,6)
And these strips (3, 6) extend along one side (3) of one conductive layer (2) and a side (6) that is diagonal to that of the other conductive layer (5). The power supplies connected to these strips (3,6) are located in the immediate vicinity of the strips (3,6) and have two points A and B belonging to the conductor layer (2,5) respectively. _A potential difference U ₁ = (V _A −V _B ) (t) is applied in the color development phase or the decoloration phase, whereby the point A in the conductor layer different from the conductor layer having the point A is applied. directly facing to that point R, between the point a, the potential difference U ₂
= (V _A -V _R ) (t) = U ₀ , wherein U ₀ is a constant potential difference selected so as to be a stable region of a coloring reaction or a stable region of a decoloring reaction. Electrochromic device. 2. The device according to claim 1, wherein the conductive strip is made of copper. 3. The device according to claim 1, wherein the electrochromic material layer comprises a cathodic electrochromic material such as tungsten trioxide. 4. The method according to claim 1, wherein the counter electrode is made of an anodic electrochromic material such as iridium oxide.
The device according to claim 1. 5. The device according to claim 1, wherein the electrolyte is a proton-conducting electrolyte. 6. The device according to claim 5, wherein the proton conductive electrolyte (8) is a polymer complex of polyethylene oxide and orthophosphoric anhydride. 7. The device according to claim 1, wherein the electrolyte (8) is a lithium conductive electrolyte. 8. A potential difference U ₁ to be applied to the time t is previously determined by the voltage-current measurement apparatus, according to claim 1
An apparatus according to any one of claims 7 to 10. 9. Apparatus according to claim 1, wherein the potential difference U ₁ = f (T) approximates an exponential function. 10. A point 'has a conductive strip (3) and the conductive strip (6 immediate neighbor to the third conductive strip (6)' of R) the voltage U ₂ between the constant So that the potential difference U ₁
Apparatus according to any of claims 1 to 7, which applies: 11. The conductive strip (6) and conductive strip (6 ') to the power supply is connected, when the voltage U ₂ is zero, a potential difference is applied to U ₃ for heating the cell , Claims
Device according to 10. 12. potential U ₃ is an alternating current, device according to claim 11. 13. effective voltage U ₃ per distance 1cm between electrodes 0.5
13. The device according to claim 12, which is V. 14. An electrochromic roof having a minimum width of more than 30 cm, wherein a switching time between a coloring state and a decoloring state is less than 1 minute at 20 ° C.
A method for using the device according to any one of the above.