JPS638890Y2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to an electrochromic display device using an electrochromic display element, in which the electrochromic display element is integrated with a quantity storage unit for controlling the quantity of electricity supplied to the display element. The purpose of this invention is to prevent electrode contamination of an electrochromic display element, thereby extending its life and improving its reliability, making it smaller, and simplifying wiring work and configuration.

In recent years, electrochromic display devices that apply electrochromism, in which the color of a substance changes reversibly through redox reactions caused by the application of voltage, are light-emitting diodes, which have good contrast and are not viewing angle dependent like liquid crystal displays (LCDs). Electrochromic display devices have attracted attention due to their many advantages such as lower power consumption than LEDs, and conventional electrochromic display devices generally have a configuration as shown in FIG. That is, a display electrode 2 made of a transparent conductive film such as a conductive NESA film is provided on the inner surface of a front substrate 1 made of transparent glass, and an electrochromism film (hereinafter referred to as EC film) such as a thin film of tungsten trioxide is placed on the display electrode 2. On the other hand, on the inner surface of a rear substrate 4 made of ceramic or resin, a counter electrode 5 of a transparent conductive film facing the display electrode 2 and a reference electrode 6 as a third electrode are provided. The front and rear substrates 1 and 4 are placed oppositely with a spacer 7 interposed therebetween, and
The electrochromic display element is sealed with an adhesive 8 such as epoxy resin, and an electrolytic solution 9 such as a dilute sulfuric acid aqueous solution is sealed between the front and rear substrates 1 and 4.
EC is configured.

Then, when the power source E is connected to the conducting polarity where the display electrode 2 has a negative potential with respect to the counter electrode 5, the electrolyte 9
The EC film 3 undergoes a reduction reaction, and the EC film 3 develops a color, and the colored state is maintained without fading even when the power source E is turned off and the EC film 3 is not energized.

On the other hand, after the color is developed, when the power source E is connected to the opposite polarity and the display electrode 2 is made to have a conductive polarity in which the display electrode 2 has a positive potential with respect to the counter electrode 5, the color is erased by an oxidation reaction.

By the way, the above-mentioned color development and decolorization are basically performed by electrochemical reactions caused by the flow of ions, so excessive voltage application during color development and decolorization may cause
If the amount of electricity applied during coloring and decoloring is different, extra side reactions will occur that will shorten the life, and the reversibility of coloring and decoloring will deteriorate, resulting in a shortened life.

Therefore, the display electrode 2 is
A device is being considered that detects the potential difference between the two electrodes 6, and drives the device while regulating the potential.
It is essentially impossible to detect and control the amount of electricity flowing between electrodes 2 and 5 from the potential difference between them.
When coloring and decoloring are repeated, contamination of the display electrode 2 can be prevented, but reaction products with extremely poor electrical conductivity gradually accumulate on the surface of the counter electrode 5.
This contamination of the counter electrode 5 shortens its life. Furthermore, if the potential regulation method is used, the drive circuit becomes complicated.

In order to prevent contamination of the counter electrode 5, it is necessary to equalize the amount of electricity required for color development and decolorization.
The idea is to control the amount of electricity that passes through the EC to extend its life.

However, in the case of a drive method that uses a capacitor to control the amount of electricity applied, there is an advantage that no reaction products accumulate on the surface of the counter electrode 5, but on the other hand, the electricity required for coloring and decoloring the electrochromic display element EC is Since the amount of electricity is several millicoulombs per square centimeter of the surface area of the display electrode 2, a capacitor capacity of several thousand microfarads is required, making it quite large, making it unsuitable for devices that require miniaturization, such as wristwatches and calculators. . Furthermore, if the amount of electricity applied during color development is stored in the capacitor for a long time, self-discharge of the capacitor cannot be ignored, and the amount of electricity applied cannot be accurately controlled.

This invention was made with the above-mentioned conventional problems in mind, and is used in an electrochromic display device that develops and erases color by controlling the conductivity between the display electrode and the counter electrode of the electrochromic display element. , on the surface of the substrate of the display element on which the display electrode or the counter electrode is formed, or on the back surface of the surface of the substrate on which the display electrode or the counter electrode is formed, a solid is formed between a pair of active materials consisting of an ionic and electronic mixed conductor having a non-stoichiometric composition. An electricity quantity storage part, which is formed by sandwiching an electrolyte and is charged and discharged by an electrochemical reaction based on the electrical conductivity, and whose voltage across both ends changes linearly according to the electricity quantity, is electrically connected to the electrodes on the formation surface. This is an electrochromic display device that is integrally formed so as to be electrically conductive.

Therefore, when coloring, the electricity storage unit is charged based on the amount of electricity passed between the display electrode and the counter electrode, and when decoloring, the charged electricity storage unit is discharged. The amount of electricity energized is controlled to be the same, preventing electrode contamination and prolonging the lifespan.In addition, the amount of electricity energized during coloring is maintained for a long time, making it possible to perform accurate energization control. and reliability can be improved.

Further, since the electric quantity storage unit is smaller than a capacitor and there is no need to provide the electric quantity storage unit in the drive circuit, the drive circuit can be simplified and downsized.

Furthermore, by integrally forming the electric quantity storage section with the display element, the device can be significantly downsized and wiring work etc. can be significantly simplified.

Next, the electrochromic display device of this invention will be explained in detail with reference to the drawings from FIG. 2 showing one embodiment thereof.

In FIG. 2, the same parts as in FIG. 1 are given the same symbols, and the display electrode 2 and EC film 3 are provided on the inner surface of the rear substrate 4, that is, on the same substrate as the counter electrode 5. Suitable materials for the display electrode 2 and the counter electrode 5 are chemically safe noble metals such as platinum and gold, or conductive NESA films such as tin oxide films and indium oxide films. Reference numeral 10 denotes a through hole formed in the rear substrate 4 below the display electrode 2 and filled with indium or the like; It is an electric quantity storage unit that is integrally formed on the back side of the surface on which display electrodes 2 are formed of the substrate 4, that is, on the outer surface of the substrate 4, and stores the first active material 11, the solid electrolyte 12, and the second active material 13 in order from the rear substrate 4. The first and second active materials 11,1 are polymerized and constituted by
As the material for No. 3, a conductor that charges and discharges depending on the polarity of electricity and whose voltage across both ends changes linearly depending on the amount of electricity flowing, that is, an ionic-electronic mixed conductor that can have a non-stoichiometric composition, such as Ag ₃ Using a PO ₄ -based silver composition and a Cu ₁ . ₈ Se copper compound, the first and second active materials 11 , 1 are used as the solid electrolyte 12 .
3, i.e., RbAg ₄ I ₅ for silver-based
(rubidium silver iodide), rubidium copper chloride, etc. are used in the copper system, and the electrochromic display element EC' is constructed as described above. Terminals A, B, and C are led out.

The drive circuit for driving the electrochromic display element EC' has a configuration as shown in FIG. That is, in the figure, 14 is a pulse input terminal, and TR ₁ and TR ₂ have their respective bases connected to the pulse input terminal 14 via the first bias resistor R ₁ .
, and their respective collectors are connected to the positive and negative terminals +V and -V of power supply E, respectively.
and PNP first and second transistors, and the emitter of the first transistor _TR1 connects to the electrochromic display element through the first load resistor _R2 .
Connected to terminal A of EC'. TR ₃ is the third NPN transistor whose emitter is connected to the emitter of the second transistor TR ₂ and whose collector is connected to the terminal A of the electrochromic display element EC' via the second load resistor R ₃ . OP is the output The terminal connects to the third transistor through the second bias resistor _R4 .
A comparator connected to the base of TR ₃ ,
One input terminal is grounded, and the other input terminal is connected to terminal B of the electrochromic display element EC'. Note that the terminals A, B, and C of the electrochromic display element EC' correspond to the terminals A, B, and C in Fig. 2, and the electrochromic display element EC' and the drive circuit perform an electrochromic display. The device is configured.

Next, the operation of the above embodiment will be explained with reference to FIG.

First, when a positive pulse +P is input to the pulse input terminal 14, the first transistor _TR1 is turned on, the display electrode 2 becomes a negative potential with respect to the counter electrode 5, and the positive terminal +V of the power source E is connected to the first transistor TR1. TR ₁ ,
A current flows through the terminal A of the electrochromic display element EC' in the direction of the terminal C, that is, from the counter electrode 5 to the electrolyte 9, the display electrode 2, and the second active material 13, and from the counter electrode 5 to the electrolyte 9. , display electrode 2,
Ions flow into the second active material 13 through the through hole 10, the first active material 11, and the solid electrolyte 12. At this time, the EC film 3 develops color, and the electricity quantity storage part M is charged, and as shown in FIG. The voltage across it changes linearly from O to h.

That is, at the time of color development, the quantity of electricity storage section M is charged, and the quantity of energized electricity is converted into voltage and stored in the quantity of electricity storage section M. At this time, comparator OP operates due to the voltage at terminal B, and the third
Transistor TR ₃ turns on.

Then, when the pulse +P is no longer input to the pulse input terminal 14 and the transistors TR ₁ and TR ₂ are turned off in the non-energized state, no current flows from the counter electrode 5 to the display electrode 2, and charging of the electric quantity storage section M is stopped. , the amount of energized electricity is stored and retained in the amount of electricity storage section M, and the EC film 3 is kept colored.

Next, a negative pulse -P is applied to the pulse input terminal 14.
When input, the second transistor TR ₂ turns on,
The display electrode 2 has a positive potential with respect to the counter electrode 5,
At this time, the third transistor TR ₃ is connected to the electric quantity storage unit M
Since the current is already in the on state due to the voltage of
A current flows from the display electrode 2 to the counter electrode 5 via the electrolyte 9, and the EC film 3 begins to be decolorized by being energized with the opposite polarity to that during color development.
The electric quantity storage section M is discharged, and the voltage across the storage section M gradually decreases from h along the characteristic curve shown in FIG.

Then, when the voltage across the electric quantity storage section M becomes 0, the comparator OP operates and the third transistor _TR3 is turned off to be in a non-energized state, and the erasing is completed.

By the way, during the period when the voltage across the electric quantity storage unit M becomes zero from the voltage across the voltage at the time of color development, the display electrode 2
The amount of electricity passed between and the counter electrode 5 is the same as the amount of electricity passed during color development.

Therefore, the amount of electricity stored in the electricity storage section M controls the same amount of electricity during color development and decolorization, thereby preventing electrode contamination and extending the service life.

In addition, since the quantity of electricity storage section M stores and holds the quantity of energized electricity through an electrochemical reaction, the drive circuit can be simplified and miniaturized compared to the case of a potential regulation method or the case where a capacitor is provided. and,
Compared to the case where a capacitor is installed, the amount of electricity applied during color development can be stored and retained for a long time, and the amount of electricity applied can be accurately controlled, significantly improving the reliability of control. be able to.

Furthermore, by integrally forming the electric quantity storage part M in the display element EC', wiring between the display electrode 2 and the electric quantity storage part M can be omitted, and in fact,
The display element EC' is provided with a plurality of display electrodes 2, as shown in FIG. As the number of electrodes 2 increases, wiring work can be simplified by omitting the wiring described above, and the device can be significantly simplified compared to when the electric quantity storage section M is externally attached to the display element EC'. Can be made smaller.

In the above example, inorganic tungsten trioxide was used as the electrochromic material.
Although an inorganic electrochromic display device in which the EC film 3 is formed has been described, an organic electrochromic display device in which the EC film 3 is not provided and organic viologen or the like is mixed into the electrolyte solution 9 as an electrochromic material may also be used. A similar effect can be obtained.

Further, an electric quantity storage section M is formed on the surface of the rear substrate 4 on which the display electrodes 2 are formed, and an electric quantity storage section M is formed on the substrate 4.
A similar effect can be obtained by forming the display electrode 2 in a layered manner and providing the electric quantity storage part M in the electrolytic solution 9. In this case, it is not necessary to provide the through hole 10.

Furthermore, in the embodiment described above, the display electrode 2 and the counter electrode 5 are formed on the same plane of the rear substrate 4;
The same effect can be obtained even if the electric quantity storage section M is formed integrally with a display device in which the display electrode 2 and the counter electrode 5 are formed to be opposed to each other as shown in FIG.

Furthermore, when there are a plurality of display electrodes 2, as described above, it is necessary to provide each display electrode 2 with an electric quantity storage part M. In this case, each electric quantity storage part M is connected to each display electrode Although it is necessary to form the electrode 2 on each formation surface or the back surface of each formation surface, for example, if only one display electrode 2 is provided, the electrode 2 must be formed on the surface where the counter electrode 5 is formed or On the back side of the forming surface, there is an electric quantity storage part M
A similar effect can be obtained by providing the following.

Next, an example of forming the electrochromic display element EC' will be specifically explained.

0.5mm on the non-conductive alumina rear substrate 4.
A through hole 10 is formed by making a φ through hole and filling it with conductive indium, and indium oxide is vapor deposited on the inner surface of the rear substrate 4 above the through hole 10, and etched in a predetermined pattern. The display electrode 2 is then formed. Then, on the outer surface of the rear substrate 4 where the through hole 10 is provided,
Ag ₂ Se-Ag ₃ PO ₄ solid solution which is the first active material 11;
RbAg ₄ I ₅ as solid electrolyte 12, second active material 13
The Ag ₂ Se−Ag ₃ PO ₄ solid solution was sequentially deposited to a thickness of 1 μm using a sputtering method, which is a type of vacuum deposition method, and etched into a predetermined pattern using nitric acid as an etchant to form the electricity storage part M. form. At this time, necessary lead wires are taken out from the electric quantity storage section M. Next, a transparent acrylic plate with a thickness of 1 mm is prepared as the front substrate 1, a spacer 7 is formed using the same acrylic plate, and the spacer 7 is sandwiched between the front and rear substrates 1 and 4, and the epoxy Seal with resin 8. Further, a mixed solution of a 0.1 mol/liter aqueous heptyl viologen bromide solution and a 0.3 mol/liter aqueous potassium bromide solution is sealed as an electrolytic solution 9.
Then, a driving circuit as shown in FIG. 3 is connected to form an electrochromic display device.

When positive and negative pulses were applied to repeatedly produce and decolorize the material, it had a lifespan of about 5 million cycles. On the other hand, for comparison, a display device of a potential regulation type in which a conventional reference electrode 6 as shown in FIG.
When decoloring was repeated, an abnormality was observed in the display of color development and decolorization after about 100,000 times.

[Brief explanation of drawings]

FIG. 1 is a partial sectional view of a conventional electrochromic display device, FIGS. 2 and 3 show an embodiment of the electrochromic display device of this invention, and FIG. Figure 3 is a wiring diagram, 4th
The figure is a characteristic curve diagram of the electric quantity storage section. 2... Display electrode, 5... Counter electrode, 11, 13
...first and second active materials, 12...solid electrolyte,
EC'...electrochromic display element, M...
Electricity storage unit.

Claims (1)

[Scope of utility model registration request] In an electrochromic display device that generates and decolors by controlling the conductivity between the display electrode and the counter electrode of the electrochromic display element,
A solid electrolyte is provided on the surface of the substrate of the display element on which the display electrode or the counter electrode is formed, or on the back surface of the surface of the substrate on which the display electrode or the counter electrode is formed, between a pair of active materials made of an ionic and electronic mixed conductor having a non-stoichiometric composition. A quantity storage unit is formed by sandwiching the electricity and is charged and discharged by an electrochemical reaction based on the electrical conductivity, and the voltage at both ends changes linearly according to the quantity of electricity supplied, and is electrically connected to the electrodes on the formation surface. An electrochromic display device that is integrally formed so as to be electrically conductive.