JPS6127525A - Driving method of electrochromic element - Google Patents

Abstract

PURPOSE:To improve the coloring efficiency, and also to realize a long life of a titled element by superposing a high frequency to an on-pulse, when driving said electrochromic element, and applying a reverse voltage of <=80% of the time of turning-on, at the time of turning-off. CONSTITUTION:For instance, when driving an electrochromic element constituted by forming the first electrochromic layer 3, an insulating layer 4 and the second electrochromic layer 6 on a transparent substrate 1 provided with the first electrode 2 consisting of a transparent electric conductor film, and forming the second electrode 5 on those films, an effective value of an applied voltage of the time of turning-on is set to +0.7-2.5V, also a high frequency is superposed to this on-pulse, and at the time of turning-off, a reverse voltage having a crest value of <=80% of the effective value of the applied voltage of the time of on is applied, and also the pulse width of the reverse applied voltage of the time of turning-off is made shorter than that of the time of turning-on. In this way, even if the effective voltage is low, a denser density is obtained substantially, and on the contrary, if the density is the same, a low driving voltage will do, therefore, a long life of this element can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to driving an electrochromic element using an electrochemical coloring/decoloring phenomenon, that is, an electrochromic phenomenon.

An electrochemical quenching dye element, that is, an electrochromic element line, which utilizes such an electrochromic phenomenon,
For example, it can be applied to numeric display elements, X-Y matrix displays, optical shutters, pattern mechanisms, etc. Classified by material, it can be divided into liquid type and solid type, but the present invention is particularly applicable to all-solid type electrochromic devices. The present invention relates to a method of driving an element.

[Background of the invention]

Two structural examples of all-solid-state electrochroic devices utilizing electrochromic phenomena are shown in FIGS. 3 and 4. These figures show the general structure of an all-solid-state electrochromic device.

The electrochromic element shown in FIG. 3 consists of a first electrode 2 made of a transparent conductor film, an electrochromic layer 3 which is a coloring layer on the anode side, an insulating layer 4 made of a dielectric film, on a transparent substrate l; The second electrode 5 made of a conductive film is sequentially laminated.

Furthermore, the electrochromic element shown in FIG.
Between the insulating layer 4 and the second electrode 5 in the structure shown in the figure,
Further, a second electrochromic layer 6, which is a coloring layer on the cathode side, is laminated.

In the above structure, the substrate 1 is generally formed of a glass plate, but this is not limited to a glass plate.
Any colorless and transparent plate such as a mirror plate or an acrylic plate may be used, and its position may be above the second electrode 5 instead of under the first electrode 2, depending on the purpose (e.g. , for the purpose of serving as a protective cover, etc.) may be provided on both sides. However, depending on these cases, it is necessary to make the second electrode 5 a transparent conductive film or to make both the electrodes on both sides transparent conductive films. If both electrodes are transparent electrodes, a transparent element can be created. The insulating layer 4 may be made of not only a dielectric but also a solid electrolyte or the like.

The transparent conductive film is an ITO film (indium oxide In2
O3 doped with tin oxide (SnO2), NESA film, etc. are used. The electrochromic layer 3, which is a coloring layer on the anode side, has conventionally been made of chromium trioxide (cr2o3), iridium oxide (IrOx), dichelium hydroxide (Nl(OH)
)2) etc. The insulating layer 4 made of dielectric material is made of zircon dioxide (ZrO2), N tantalum pentoxide (Ta□05), silicon oxide (sto, sto□).
), or lithium fluoride (L
iF), 7, magnesium oxide (MgF2), and the like. Further, the electrochromic layer 6, which is a coloring layer on the cathode side, is made of tungsten oxide (W).
O2, WO3), molybdenum oxide (MOO2, MOO3)
) Formed using vanadium pentoxide (V2O5) or the like.

In an all-solid-state electrochromic device having such a structure, a vapor chemical reaction occurs when a voltage is applied between the first electrode 2 and the second electrode 5, and the stain is colored or decolored. It is generally said that this coloring mechanism is based on bronze formation due to mesyl injection of cations and electrons into the electrochromic layer 6, for example. For example, when WO3 is used as an electrochromic substance, an oxidation-reduction reaction represented by the following formula (1) occurs, resulting in coloration.

WO3+ xH++ xs-RHXWO3, (1) (1
According to the formula ), tungsten bronze HxWOs is formed and colored, but if the applied voltage is reversed, the color becomes decolored. In an all-solid-state electrochromic device, such a reaction of formula (1) causes coloration due to the supply of protons H+ by an insulating layer inside the device.

In the electro-Iff chromic element described above, the electrochromic layer 3, which is the coloring layer on the anode side, is conventionally formed of an oxide such as iridium oxide (IrOx) by a reactive sulfur oxide film method or an anodic oxide film method.

[Problem that the invention seeks to solve]

The present invention relates to a method of driving an electrochromic element having the structure shown above. Electrochromic elements deteriorate as they are used, and the deterioration of the electrochromic elements is, for example,
In order to increase the coloring density, when trying to increase the amount of charge by increasing the applied voltage or lengthening the application time, the film peeled off due to gas generation due to decomposition of H2O, and the injection of protons into WO3 One of the causes is thought to be an incomplete reverse reaction due to over-washing.

The present invention aims to extend the lifespan of an electrochromic element, and in view of the above-mentioned causes, it is an object of the present invention to provide a driving method that has good coloring efficiency and can further extend the lifespan even though the effective voltage is the same. The purpose is to

[Summary of the invention]

The method for driving an electrochromic device according to the present invention includes:
A first electrochromic layer 1. on a transparent substrate with transparent electrodes. When driving an electrochromic element formed by forming an insulating layer and a second electrochromic layer and forming electrodes on these films, the effective value of the applied voltage at the time of ON is set to +0.7 to 2.5 ■. , and a high frequency is superimposed on the ON p4 pulse, and when OFF, a reverse voltage having a peak value of 80% or less of the effective value of the applied voltage when ON is applied, and the pulse width of the reverse applied voltage when OFF is the same as when ON. It is also characterized by its short length.

[Embodiments of the invention]

As shown in FIG. 4, the present invention provides a first electrochromic layer 3, an insulating layer 4, and a second electrochromic layer 6 on a transparent substrate 1 provided with a first electrode 2 made of a transparent conductor film. When driving the electrochromic device formed by forming the second electrode 5 on these films, the effective value of the applied voltage when turned on is determined using a driving voltage with a waveform as shown in FIG. +0.7 to 2.5V, and the ON )4
Superimposing a high frequency on the pulse 1. When OFF, a reverse voltage having a peak value that is less than a factor of 80 of the effective value of the applied voltage when ON is applied, and the Noculus width of the reverse applied voltage when OFF is shorter than that when ON.

In FIG. 1, voN indicates the applied voltage when ON, vH indicates the high frequency superimposed thereon, and voFF indicates the reverse applied voltage when OFF. Here, voN is 1.0 ~ 21VXVH is ~
0.6v1voFF is preferably in the range of ~1.5■, and the high frequency superimposed on voN is preferably between 1 kHz and 10 MHz, although it depends on the width of ta.

By using the waveform shown in Figure 1, even if the effective voltage is low, a substantially higher concentration can be obtained; conversely, if the concentration is the same, the driving voltage can be lower. Therefore, a longer life can be achieved.

Further, the reason why the applied voltage for decoloring has a shorter pulse width and smaller peak value than the applied voltage for coloring is to prevent excessive reverse reaction, thereby extending the life.

The waveform shown in Figure 1 is the general 0MO8 or "
It can be easily formed with a logic circuit using rTL.

FIG. 2 shows its block diagram. The operation will be briefly explained below. A basic clock pulse is generated by an oscillator 11 and inputted to a monostable multivibrator 12.13. The monostable multivibrators 12 and 13 are each
The basic clock/4 pulses act on rising and falling,
Controls the pulse length on the positive and negative sides. - The blade high frequency oscillator 14 generates a pulse that satisfies the above conditions and inputs it to the signal synthesis circuit 15. The signal synthesis circuit synthesizes the high frequency pulse and the output from the positive side monostable multivibrator. The display 16 is driven by applying the output from the signal synthesis circuit on the positive side and the output from the monostable multivibrator on the negative side.

Example 1 An electrode made of an ITO film was formed on a transparent substrate, having appropriate extraction electrode parts and lead parts.

On top of this, an Irox film as a first electrochromic layer was formed by sputtering, and a Ta 205 film as an insulating layer and a WO3 film as a second electrochromic layer were further formed by vacuum evaporation. , a semitransparent AU film was formed as the upper electrode.

■This electrochromic element. , = 1.5
VvH=0.4v, vOFF=1.0V, ta=20Qmsec t(B=Otb=1
00 m5ec, the color density change is ΔO,D
0.2, the repeat life is 8 x 10 times, conventional +
7) V. N=, 1.5 V V, =c OV V
The driving method of o, , = -1.5 V, t, = tb = 200 msec also improved the life by more than one order of magnitude.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the waveform of the driving voltage used to carry out the method of the present invention, FIG. 2 is a schematic diagram of the circuit used to form the waveform shown in FIG. 1, and FIG. 4 and 4 are cross-sectional views showing two examples of electrochromic devices. 1... Substrate 2... First electrode 3...
Electrochromic layer 4... Insulating layer 5... Second electrode 6...
Electrochromic layer 11... oscillator 12, 13... monostable multivibrator 14...
High frequency oscillator 15... Signal synthesis circuit 16... Display (Figure 1 Cl1II Zulus) Figure 3 Figure 4

Claims (1)

[Claims] When driving an electrochromic element in which a first electrochromic layer, an insulating layer, and a second electrochromic layer are formed on a transparent substrate provided with a transparent electrode, and electrodes are formed on these films, ON The effective value of the applied voltage at the time is set to +0.7 to 2.5 V, and a high frequency is superimposed on the ON pulse, and at the time of OFF, a reverse voltage having a peak value of 80% or less of the effective value of the applied voltage at the time of ON is applied. Apply and OF
A method for driving an electrochromic element, characterized in that the pulse width of the reversely applied voltage when F is shorter than that when it is ON.