JPH05100628A - Electrochromic element drive system - Google Patents

Abstract

(57) [Summary] [Purpose] To prevent the occurrence of color residue or color unevenness of the electrochromic element and to dramatically improve the cycle characteristics. [Structure] A capacitor is connected in series to the electrochromic element, and coloring voltage and decoloring voltage are repeatedly applied through the capacitor to repeat coloring and decoloring. Also, immediately after the voltage is applied, a resistor is inserted in series to the capacitor and the voltage is applied. By driving while suppressing the voltage immediately after the application, it becomes possible to prevent the occurrence of color unevenness and color residue and to dramatically improve the cycle characteristics.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrochromic device (ECD) and, more particularly, to an electrochromic device driving method which does not cause uneven color or residual color even after repeated use.

[0002]

2. Description of the Related Art At present, a liquid crystal display element with low power consumption and high response speed is used for display of calculators, watches, etc., but since polarized light is used as a display mechanism, it has viewing angle dependency, Further, since only black and white display is possible, eye fatigue cannot be ignored when used for a long time like a computer or an OA device. Therefore, as a new display element replacing the liquid crystal display element, an ECD in which the color of a substance reversibly changes upon application of a voltage is drawing attention.

Since the ECD uses ordinary light which does not depend on the viewing angle, it causes less eye fatigue, has low power consumption, has a memory property, and is capable of displaying a large area. Some have already been put into practical use as large display boards such as stock price displays, message boards, guide boards, and display elements or light control elements such as automatic antiglare mirrors, light control glasses, and sunglasses.

Such ECD will be described with reference to FIG. FIG. 7A shows an example of a reflection type ECD, in which a thin film of a current collector (ITO) 32 is formed on a transparent glass 31 by a reactive sputtering method or the like, and a tungsten oxide (WO ₃ ) film is formed thereon as a display electrode. 33 is formed by vacuum vapor deposition or the like, and a glass plate 37, a counter electrode 36, and a counter electrode 36 are provided on the opposite electrode side with the electrolyte 34 interposed therebetween.
The background plate 35 has a laminated structure. When a DC voltage is applied to such an element between the ITO 32 and the counter electrode 36 so that the ITO 32 side is (−) from the power source (not shown), an ionic current flows through the electrolyte 34, and as a result, a reduction reaction occurs in WO ₃ 33, The light absorption property of WO ₃ changes to develop color. Therefore, the color development of WO ₃ can be observed by observing the reflected light from the glass 31 side. When both electrodes are short-circuited, an electric current flows in the opposite direction, an opposite reaction occurs, and the color disappears.

FIG. 7B shows an example of a transmissive ECD.
Without providing the background plate of FIG. 7A, the display layer 40 (for example, iridium oxide that develops color by an oxidation reaction), ITO 41
By observing the transmitted light from the glass 37 side, it is possible to observe the color development in which WO ₃ and the display layer are subtractively mixed.

[0006]

As described above, the ECD is colored by the oxidation and reduction reactions, but the color is thin immediately after the application of the DC voltage because the degree of the reaction is small, and the color becomes dark as the integrated amount of the current increases. Then, the reaction saturates and a constant concentration of color is developed. In this state, the ionic current is almost zero, and a kind of secondary battery is formed between the oxidation electrode and the reduction electrode, in which energy corresponding to the amount of electricity is stored. Therefore, when both electrodes are short-circuited, a discharge occurs and the oxidation and reduction electrodes cause a reaction opposite to that at the time of color development, resulting in decolorization. Therefore, as shown in FIG. 8, when a voltage is applied and a short circuit is performed in a cycle of about 5 seconds, coloring and decoloring are repeated. By the way, if coloring and erasing are repeated a number of times, color unevenness and color residue occur, and it becomes unusable, and conventional ECD has a limit of about 2000 times at most.
There was a problem that the cycle characteristics were not good.

The present invention is intended to solve the above problems, and an object of the present invention is to provide an electrochromic device driving method capable of preventing the occurrence of color residue and color unevenness and dramatically improving the cycle characteristics. And

[0008]

SUMMARY OF THE INVENTION The present invention focuses on the fact that color unevenness and color residue easily occur when driven at a high voltage or when a voltage of the same voltage is applied for a long time. When they were connected in series and driven, the cycle characteristics could be dramatically improved. Figure 1
Is a diagram for explaining the driving method of the present invention, and FIG. 2 is a voltage waveform diagram. In the figure, 1 is an ECD, C is a capacitor, E is a DC power supply, and S1 is an on / off switch.

In FIG. 1, ECD1 has the same structure as that described with reference to FIG. 7, and the electrolyte is not particularly limited, but the problems of liquid leakage and evaporation of the electrolyte of ECD are solved, and the area is enlarged and laminated. It is desirable to solidify the electrolyte layer into a thin film from the viewpoint of easiness of handling and handling, and such a thin film is specifically prepared by filling and fixing the electrolyte dissolved in an organic solvent in the pores of the polymer porous film. can get. The polymer film is made of polyolefin, polyester, polycarbonate, polytetrafluoroethylene, polyvinylidene fluoride, or the like and has a film thickness of 0.1 to 50 μm and a porosity of 40 to 90.
%, Average pore size 0.001 to 0.1 μm, breaking strength 200
It is more than kg / cm ² . As an electrolyte, an alkali metal salt, particularly halogenated Li, LiClO ₄ , LiC
Li salts such as F ₃ SO ₄ are suitable. Further, as the organic solvent, propylene carbonate (PC), low molecular weight polyalkylene oxide or their ether compounds, benzaldehyde, benzonitrile, benzyl alcohol,
Examples are dibenzyl ketone, diphenylpropionitrile and the like.

A capacitor C is provided for such an ECD1.
Are connected in series. The capacitor to be connected may have any capacity, but, for example, 0.001 to ¹ cm ² of ECD
It should have a capacity of 0.02F. Then, the switch S1 is turned on by the on / off device 2 including a timer.
Is turned on / off at intervals of, for example, 5 seconds to apply a DC voltage,
Due to a short circuit, the ECD 1 is repeatedly energized / discharged through the capacitor C. The voltage applied to ECD1 at this time is as shown in FIG. That is, immediately after the switch S1 is turned off, the voltage of the power source E is directly applied to the ECD, but since the capacitor C is charged, the charging voltage increase CV is E
The voltage applied to CD exponentially decreases, an exponentially decreasing current flows between the electrodes, and coloration occurs due to the oxidation / reduction reaction. When the switch S1 is turned on after 5 seconds, the charging voltage CV of the capacitor C is applied in the opposite direction, the energy stored in the ECD and the capacitor are discharged at the same time and a decoloring reaction occurs, and eventually the voltage applied to the ECD becomes 0 and completely. Erase.

By such driving, it was possible to prevent color unevenness and color residue from occurring at least 10 times or more as compared with the conventional one, even if the coloring / decoloring cycle was repeated. This is because the voltage applied to the ECD is reduced by the charging voltage of the capacitor and the capacitance of the capacitor is E.
It is considered that one of the reasons is that the capacitance of the CD is connected in series, so that the overall capacitance becomes smaller, the time constant becomes shorter, and the time during which the current flows becomes shorter.

FIG. 3 is a diagram showing another example of the present invention. In FIG. 3, the resistor R is connected in series to the capacitor C only immediately after the voltage is applied. That is, even if a capacitor is connected, the power supply voltage is directly applied to the ECD immediately after the voltage is applied. Therefore, a resistor R is connected in series to the capacitor C, and a switch S2 for short-circuiting the resistor R is provided, and the on / off device 2 is interlocked with the power source applying switch S1. As shown in FIG. Is turned off and the switch S2 is turned on immediately after the power supply voltage is applied to short-circuit the resistor R. The resistor R is connected only for the time Δt immediately after the voltage application, and as a result, E
As shown in FIG. 4B, the voltage waveform applied to the CD1 has a suppressed voltage value when the voltage is applied, and the cycle characteristics of the ECD can be further improved.

[0013]

In the present invention, a capacitor is connected in series with the ECD, and a voltage is repeatedly applied through this capacitor. As a result, compared with the conventional one,
Even when the coloring / erasing cycle is repeated at least 10 times or more, color unevenness and color residue are prevented from occurring, and the cycle characteristics can be dramatically improved.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 5A, IT of about 10 Ω / □
On the glass 11 coated with the O film 12 to a thickness of 2000 liters, WO ₃ 13 was deposited to 5000 liters by an electron beam evaporation method. Similarly, the ITO film 16 (20
00Å) was coated to deposit 4000Å of NiO.
As the thin film electrolyte 14, a solid polymer porous film having a film thickness of 25 μm and a porosity of 70% filled with an ionic conductor is used, and as shown in FIG. Variable color part 40 fixed with agents 18 and 19
A cm ² ECD was produced. Next, as shown in FIG. 6A, the capacitor C is attached to the ECD 22 of the variable color portion 40 cm ^2.
Was connected in series and colored with a DC power supply 21 at 2.4 V for 5 seconds and then decolored at 0 V for 5 seconds. As a result, problems such as color unevenness and color residue did not occur even after being cycled 50,000 times.

[Comparative Example] In contrast, an EC having the same structure
A conventional drive circuit as shown in FIG. 6B, in which D is used and a capacitor is removed from the circuit of FIG.
When a cycle test of coloring with sec and erasing with 0 V for 5 seconds was performed, it was possible to obtain the coloring and the transparency at the time of erasing in the same degree as in the case of FIG. 6A.
Even when the voltage was lowered with respect to (a), color unevenness occurred in about 2000 cycles.

[0017]

As described above, according to the present invention, a capacitor is connected in series to the ECD and coloring and decoloring are repeated, so that the life of the ECD is significantly extended and unevenness in color and color can be prevented. It is possible to achieve the remaining significant suppression.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a drive system of the present invention.

FIG. 2 is a voltage waveform diagram.

FIG. 3 is a diagram showing an example in which a resistor is inserted in a capacitor.

FIG. 4 is a voltage waveform diagram.

FIG. 5 is a diagram illustrating an ECD used in Examples.

FIG. 6 is a drive circuit diagram of an example and a comparative example.

FIG. 7 is a diagram illustrating a structure of an ECD.

FIG. 8 is a voltage waveform diagram of a conventional driving method.

[Explanation of symbols]

1 ... ECD, C ... Capacitor, E ... DC power supply, S1 ... On / off switch.

Claims (2)

[Claims] 1. A driving method in which a voltage is applied to an electrochromic element having a display electrode formed on at least one side with an electrolyte sandwiched between the electrodes to cause current to flow / discharge, and coloring and decoloring are repeated. An electrochromic device driving method characterized in that a capacitor is connected in series with the capacitor, and electricity is supplied / discharged through the capacitor. 2. The electrochromic element drive system according to claim 1, further comprising a resistor inserted in series with the capacitor for driving only when the energization is started.