JPH0356943A - Electrochromic system and method of using the same - Google Patents

Abstract

PURPOSE: To make it possible to control the brightness of the sunshine in a building or automobile and more particularly a vehicle provided with a glass roof by controlling light transparency by impressing potential on the terminals of a transparent glass system of an electrochromic type. CONSTITUTION: The glass plate 1 is covered with a transparent conductor layer 2 and has a band-shaped body 3 for current introduction. The glass plate 4 facing the same is coated similarly with a transparent conductor layer 5 and has a band-shaped body 6 for current introduction. the system has an anodic electrochromic material layer 7, a proton conductive electrolytic layer 8 and a cathodic electrochromic material layer 9. A potential difference U1 =VA-VB(t) is applied between the points A and B of the conductor layers 2, 5 and further, a potential difference U2 =(VA-VB)(t)=UO is applied between the points R directly facing the point A and A so that the UO exists in the stable region of color development reaction or exists in the stable region of decoloration reaction. As a result, the switching time iterating between the colored state and the decolored state even at the size of the glass windows of the building and automobile, is made shorter.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to electrochromic systems, particularly electrochromic transparent glass systems, and more particularly to glass systems whose light transmittance is adjusted by applying a potential to terminals of the glass system. According to 89 400 814, the glass of the present invention reduces the brightness of sunlight inside a building or a motor vehicle, in particular a vehicle with a glass roof. A cathodic electrochromic material such as tungsten oxide (IAO3) and a proton-conducting electrolyte such as polyethylene oxide (POε
An electrochromic glass system is known in which a copolymer complex of 1.2%, orthophosphoric acid, and an anodic electrochromic material such as iridium oxide are sequentially arranged. Protons can be reversibly introduced into the two glass plates in contact with the electrolyte by applying an appropriate voltage to opposite ends of the glass system, and the introduction reaction into the tungsten oxide layer involves protons from the iridium oxide layer The iridium oxide layer acts as a counter electrode to the tungsten oxide layer. Thermodynamic equilibrium can be written as:

WO3+xf{++xe- <---> HxWO
．． and HxlrOy<-->boy+xH"+xeThe instantaneous measurement of the current strength I across the glass layer is a direct measurement of the number of points at which proton introduction and removal reactions occur at that instant.

The applied potential difference 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 coloring or decoloring occurs. However, if a predetermined voltage is exceeded, there is a risk that a side reaction may occur and protons may be reduced to hydrogen molecules or water remaining in any layer may be oxidized to oxygen.

Considering the interfacial overpotential, the limit range of the characteristic electrochemical stability of the above system is 0.6 to l. 5 V, and -0.
It is 6~Ov. Hereinafter, these limit ranges will be referred to as "electrochemical stability regions for coloring and decolorizing reactions."

A second problem is the time required to develop or decolorize the desired color. This means that, assuming maximum color development and decolorization, the time required for the electrical load to pass through for all reaction potential points, in other words, the current intensity I decreases to zero, or at least reaches zero. This is the time required for the value to decrease to a close value.

As the size of the cell increases, the amount of electrical load passed through it increases correspondingly. However, the current intensity cannot be increased proportionally. It follows that by the theoretical relationship between the potential difference V and the current I, I is This is because it becomes smaller than V/R. For small size cells, the RI is very small, and as the cell size increases, the RI increases rapidly and the voltage drop across the ohmic resistance becomes the limiting factor for the current and therefore the rate of color development and decolorization.

In a light-transmitting cell, it is not possible to choose a material as the transparent conductor layer whose square resistance is less than, for example, 1 ohm. Most currently used materials and deposition techniques are only capable of achieving layers with a square resistance of 2 to 5 ohm. However, the current flow is masked by strings that form non-point strips or lines of conductor extending along opposite sides of the cell and form a frame around the glass system to prevent leakage. This limit can be partially exceeded using introducers. This strip or wire conductor can be selected from a good conductor, such as copper, in which all points on the same strip are at equal potential. As a result, if the glass-based surface is placed in a virtual coaxial system xy in which the horizontal axis X is parallel to the band-like body of the current introducing body, all points where y is the same have an equal potential. On the other hand, two points having the same horizontal axis X and different vertical axes have different potentials if the distances from the central axis, which is the axis of symmetry of the cell, are the same.

In fact, the distance between two strip-shaped conductors is, for example, 10 cm.
, the cell switching time exceeds 1 minute.

Of course, this distance can be subdivided by increasing the number of conductive strips. For a glass system with a width of l,
As before, when one conductive strip is at y=o and the second strip is at y=1, the strips are placed at y=1/3・l and y=2/3・l, Add by changing the contact surface. A cell thus shaped is equivalent to a collection of three identical subcells placed in parallel, each subcell having a resistance that is one-third lower. However, when combined like this,
The conductive strips become reticulated and spoil the overall appearance of the glass system.

Electrochromic glass systems do have a light-transmitting effect, but other electrochromic glass systems of the mirror or display type necessarily have at least one transparent conductor layer with relatively low electrical conductivity compared to, for example, dense metal layers. Kuromifuku type also has light transmittance.

Furthermore, whatever the mode of action of electrochromic systems, i.e. the introduction of protons or other cations, or the reduction/dissolution of metal salts, for example, we find similar problems due to voltage drops due to ohmic resistance. Dew.

In the present invention, even if the width of the glass system is about 50 cm, which corresponds to the size of a glass window of a building or an automobile, the time required to repeatedly switch from a colored state to a bleached state is 3.
The aim is a large-area electrochromitter system that is shorter than 0 seconds.

This technical problem consists of two glass plates (1, 4) each coated with a conductor layer (2.5), an electrochromic material layer (9) and an electrolyte (8), and a counter electrode (7). )
and the conductive layer (2.5) each has a conductive strip (3.6) made of a material having a conductivity greater than that of the conductor layer (2.5); 3.
6) are placed along the opposite sides of the glass system, and the power supply connected to these strips (3.6) is connected to the strips (3 or in the decolorized phase, the potential difference U, = (V & VB )N)
is applied, and as a result, a potential difference [2'' (VA - Vl1 ) (
t) = UO and is configured to be a constant potential difference chosen such that U0 is in the stable region of the color-developing reaction or in the stable region of the decolorizing reaction. Ru.

The voltage drop across an ohmic resistor is directly related to the distance between the electrodes and is generally worked using conductive strips running 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 with the present invention different conductivities are applied on the same side of the glass system. A potential difference is applied between two points placed on the body layer with the same abscissa axis. According to this method, the effective voltage is maximum at time t=0, and from this fact the observer perceives color development or decolorization more quickly. It should be noted that the proposed voltage application cannot actually compensate for the voltage drop due to ohmic resistance. In this way, the voltage difference U. If V is applied from one side of the glass system, the potential difference V (y) between two facing points is always lower than the applied voltage, except at the edges of the glass system (y=0 or y=1>). However, according to experimentally confirmed results, this value V (
y) is the vO between the two bands at the edge of the glass system of UU0.
is always higher than the value V' (y) obtained when .

As a result, maximum color development can be obtained very quickly, with a total response time of 3
It can be about 0 seconds.

Compared to previously known electrochromic glass systems, the glass system of the present invention has a very significant difference between the transient color state in the peripheral region and the transient color state 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 position of these points, as mentioned above. However, whatever the position, the effective potential difference is much higher than in 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 becomes blue-black very quickly, but the central color development does not appear until the end of the switching time. However, of course, from this moment on, the glass color becomes completely uniform.

According to a first embodiment of the invention, the potential difference U to be applied at time t in order to obtain a constant potential difference U2 over time
What t should be is determined in advance by a voltage-current measuring and recording device. Once these values are determined, a power supply can be designed based on these values.

To simplify this design, we use the curve U+ f (t
) can be approximately taken as an exponential function.

This simplifies the electronic components connected to the voltage generator, but eliminates the need for testing each glass-based model to determine its true size in order to determine the parameters of the exponential function. isn't it.

In order to obviate this difficulty in advance, it is preferable to use a three-electrode assembly of the type of a potentiostatic device, for example a practical amplifier. To do this, place a reference electrode at point R. For the problem of balancing electrical loads, if the position of this reference electrode is on the straight line y=0, then all points on this straight line are at equal potential. Therefore, when the reference electrode R is composed of the entire length of the glass system or a conductive strip of the length of the glass system, the reference electrode R is formed of two parallel conductive strips of one of the two glass plates. It is preferable to place an electrode on each side. This assembly can overcome another drawback of electrochromic glass systems, namely the very low reactivity at low temperatures, especially below XO<0>C. In this case, when a potential difference is applied between the two electrodes, the transparent conductor layer located between the two electrodes can be used as a heating layer due to the release of heat generated by its resistance.

The potential difference applied for this preheating exceeds 20V and 24
A value of about V is preferable, and this value is generally determined by the distance between the electrodes l c
It corresponds to a voltage gradient of about 0.5v per m. This preheating phase, for example, precedes all color development and lasts about 2 minutes.

Considering the vicinity of the second glass plate, there is a tendency for the colored phase to become bluish over time, but this can be avoided by using alternating current.

Other advantageous features of the invention will become apparent from the following description with reference to the accompanying drawings.

FIG. 1 is a diagram showing the principle 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 thickness ratios of the various members of the system have been varied in the figures. The configuration of this cell is as follows. The glass plate 1 is coated with a transparent conductive layer 2 and has a band 3 for introducing current. Preferably, this strip 3 is parallel to the direction of the length L of the glass system. Note that the width of the glass material is l. The glass plate 1 faces a second glass plate 4, which is also coated with a transparent conductor layer 5,
It has a band-shaped body 6 for introducing current. two transparent conductor layers 2
and 5, a layer 7 of an anodic electrochromic material, preferably iridium oxide, a proton-conducting electrolyte layer 8, preferably a copolymer complex of polyethylene oxide and strictly anhydrous orthophosphoric acid; and a layer 9 of cathodic electrochromic material, preferably tungsten oxide.

For purposes of illustration, we will use layers with the following defined properties.

Substrate (1.4): Float glass plate with a thickness of 3111 [D] Transparent conductor layer (2.51 tin-doped indium oxide layer deposited by magnetron cathode sputtering, thickness 4000 m square resistance 5 ohm cathodic electrochromic layer. 9): 5 x 10
Tungsten oxide layer, thickness 260 nm, deposited by vapor deposition of molybdenum in vacuum air at -'Torr Electrolyte (organic polymer 8): Method for producing a solid solution of phosphoric anhydride in polyethylene oxide in strictly anhydrous, pure 17.5 g of phosphoric acid and polyethylene oxide having a weight average molecular weight of 5,000,000 were dissolved in 1 liter of solvent. Density l. 21, glass transition point -40
°C, ratio of the number of oxygen atoms in the polymer to the number of hydrogen atoms in the acid ○/H
0.66.

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

This solution was allowed to flow down onto a glass plate coated with a tungsten oxide layer deposited as described above.

The thickness could be made uniform by the doctor blade method.

The solution flow is carried out in a humidified atmosphere, preferably at a humidity of 40-100 ppm, which optimizes the contrast subsequently obtained.

Anodic electrochromic layer; iridium oxide layer deposited by cathode sputtering with a gas mixture of oxygen/hydrogen (80:20) at 6 mTorr and a magnetic field, thickness 55 nm 0 The electrolyte layer was deposited immediately after depositing the tungsten oxide layer. ,
Preferably it is deposited on top of this layer.

15kg/cff of glass aggregate in autoclave
Heat to 90°C under pressure.

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

By conventional methods, a region of stability for the desired electrochemical reaction is created between a point A, which can be considered as a point on the conductive strip 3, and a point B, which can be considered as a point on the conductive strip 6. Apply a selected fixed potential difference, V,. Such an aggregate is divided into three similar cells Sl, 32 and S3.
used for. In these cells, the spacing between the current conducting strips was 3, 4.5 and 9C[II, respectively.

FIG. 3 shows how the coloring current intensity changes over time. For the two small cells, the current IO at t=Q 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 cell 3, the current 1o is not proportional to the surface and is limited by the voltage drop caused by the ohmic resistance. In fact, this can only be achieved in cells with current conducting strip spacings greater than 10 cm, unless switching times longer than 1 minute are accepted.

Another way to analyze this problem is to calculate (X・y・a) and (x
,y,b), consider two points MA and M,.

Between these two points, at time t, the potential difference is V=V
MA - VMa.

However, if we choose a conductive strip 3.6 of copper or any other good conductor, we can consider every point MA or Mn on a given ordinate axis y to be at a conductive potential, respectively. In FIG. 4, a curve 10 represents the variation of the value of V as a function of the ordinate axis y with the spacing of the combination of points MA and M8. A potential difference UI of 1.4 V is applied to a cell with a distance of 14 cm between points A and B, and it is determined that the effective voltage V at t = 0 is extremely lower than U1, and that the difference between these voltages is Indicates that it is significant.

Keep, U2 = 1. Curve 11 is obtained as 4V.

It should be noted that for all combinations of points MA and MB, the observed potential difference V is always less than or equal to U2. For a given electrochemical reaction, it is a necessary and sufficient condition to apply a potential difference value U2 that lies in the electrochemical stability region of the invention. Other than the top of the side,
The effective voltage is not equal to the applied voltage U2. The present invention cannot completely eliminate voltage drops due to ohmic resistance. However, a comparison of curves 1O and 11 shows that the effective voltage curve 11 of the present invention is approximately three times as large as curve 10 for all combinations of points MA and M.

As a result, coloring or decoloring occurs extremely quickly. Furthermore, we have demonstrated that the edge effect is more pronounced than in prior art combinations, with current being transmitted almost instantaneously near the edge of the glass system, but slower in the central region. A feature of the present invention is that color development progresses from the edges.

Terminals A with a spacing of 14 cm. For B, the color development time gain is 6 seconds, which is a 30% time gain.

For terminals that are more widely spaced than this, the gain increases further. In this way, the short side of the electrochromic ceiling is 30cm
m and the switching time can be less than 1 minute at 20°C. In this case, by dividing the switching time by 6, the switching time can typically be reduced from 3 minutes to 30 seconds.

In the assembly of the present invention, two current-introducing strips 66' are provided in the conductive layer 5. The electrical resistance of the conductor layer 5 can be used to heat the cell.

For this purpose, before color development, a potential difference U3 is created between point B and point R.
For example, 24V is applied, thereby increasing the temperature of the electrolyte layer. Maximum performance is obtained when this temperature is between 20 and 80°C. Potential difference U3 is preferably an alternating current to avoid polarization of the electrochromic material layer, in which case the effective voltage is, for example, 24V. However, it should be noted that heating can be used regardless of the oxidation state of the electrochromic material layer.

As mentioned above, although the invention has been described with respect to cells with proton-conducting electrolytes, it is understood that the invention can also be applied, if desired, to cells containing all electrochromic systems, especially ion-conducting electrolytes such as lithium. should be understood. Similarly, other materials, such as those mentioned above, can be used to realize the electrochromic layer and the counter electrode, in particular with the aim of obtaining other color tones, and by adjusting the value of the pre-applied voltage, new Thermodynamic equilibrium can be activated. Furthermore, the assembly with three electrodes can be used in all systems that require at least a transparent conductor layer, such as systems that act by the introduction and removal of ions called in memory, electrochromic gel systems, or liquid crystal displays. It can be widely used in various systems.

[Brief explanation of drawings]

Fig. 1 is a perspective view showing the principle of the electrochromic cell of the present invention, Fig. 2 is a cross-sectional view of the glass ceiling of an automobile, and Fig. 3 is a diagram illustrating three cells with different intervals between current introducing bodies over time. FIG. 4 is a graph showing changes in coloring current over time, and FIG. It is a graph showing the relationship between the interval of Ma combinations (coordinate axis y) and effective voltage. 1.4-...Glass plate, 2.5 ridge conductor layer, 3.
6... Conductive strip, 7... Counter electrode, 8...
Electrolyte, 9... Electrochromic material, 10... Cell of prior art, 11... Cell of the present invention. To OCD ω size

Claims (1)

[Scope of Claims] 1. Two glass plates (1, 4) each coated with a conductor layer (2, 5) are coated with an electrochromic material layer (9).
), an electrolyte (8), and a counter electrode (7), and a conductive strip ( 3,6)
These strips (3, 6) are arranged along opposite sides of the glass system, and these strips (3, 6) are arranged along opposite sides of the glass system.
6), in the direct vicinity of the strip (3, 6), between the two points A and B belonging to the conductive layer (2, 5), in the coloring phase or the coloring phase. A potential difference U_i=(V_A-V_B)(t) is applied, thereby causing a difference between point R, which is on a conductive layer different from the conductive layer where point A is located and directly facing point A, and point A. In between, give a potential difference U_2=(V_A-V_R)(t)=U_0,
An electrochromic system configured such that U_0 is a constant potential difference selected such that it is in the stable region of color-developing reactions or in the stable region of decolorizing reactions. 2. The system according to claim 1, wherein the conductive strips (3, 6) consist of copper. 3. System according to claim 1 or 2, wherein the electrochromic material layer (9) consists of a cathodic electrochromic material, such as tungsten trioxide. 4. Claim 1, wherein the counter electrode (7) is composed of an anodic electrochromic material such as iridium oxide.
3. The system according to any one of 3 to 3. 5. The system according to any one of claims 1 to 4, wherein the electrolyte (8) is a proton-conducting electrolyte. 6. The system according to claim 5, wherein the proton conductive electrolyte (8) is a copolymer complex of polyethylene oxide and orthophosphoric anhydride. 7. The system according to any one of claims 1 to 4, wherein the electrolyte (8) is a lithium ion conductive electrolyte. 8. The system according to any one of claims 1 to 7, wherein the potential difference U_1 applied at time t is measured in advance by a voltage-current measuring and recording device. 9. The system according to claim 1, wherein the potential difference U_1=f(t) approximates an exponential function. 10. Directly near point R, third conductive strip (6')
and the voltage U between conductive strips (3) and (6')
8. The system according to claim 1, wherein the potential difference U_1 is applied such that_2 is constant. 11. System according to claim 10, characterized in that the power supply connected to the conductive strips (6, 6') applies a potential difference U_3 which is used for heating the cell when the voltage U_2 is zero. 12. The system according to claim 11, wherein the potential difference U_3 is an alternating current. 13. The effective voltage U_3 is 0.0 for every 1 cm of distance between the electrodes.
13. The system of claim 12, which is 5V. 14. Switching time between coloring state and decoloring state is 20℃
Claims 1 to 1, wherein an electrochromic roof having a minimum width of more than 30 cm is realized in less than 1 minute.
3. A method of using the system according to any one of 3.