JPS6332164B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrochromic (hereinafter referred to as EC) display device using an electrochemical coloring substance.

The electrochemical color forming substance used in the present invention is:
It is a substance that changes color when an electric field is applied, and exhibits a phenomenon in which optical properties depend on electrical polarity, and is generally called an EC substance.

Conventional EC display devices have much superior display clarity compared to non-emissive liquid crystal display devices, but they have drawbacks such as slow response, high power consumption, and difficult driving methods.

Figure 1 shows the general structure of a conventional EC display device. The two upper and lower substrates 1 and 2 face each other with a spacer 3 in between to form a cell. The upper substrate 1 is made of transparent glass, and a transparent conductive film 4 made of indium oxide or the like is provided on the inner side of the cell, and an electrode 5 made of an EC material such as tungsten oxide or molybdenum oxide is further formed thereon. The lower substrate 2 is made of glass,
A substrate made of ceramic or the like is provided with a metal such as gold or platinum or a conductive material such as indium oxide on the inner side of the cell to form a counter electrode 6. An electrolytic solution 7 containing an electrolyte such as sulfuric acid or lithium perchlorate dissolved in a solvent is sealed between the upper and lower two substrates 1 and 2, and a powder such as titanium oxide or powder such as titanium oxide or the like is used as a white background for coloring and decoloring the EC material. A porous white plate is included.

In the conventional EC display device having the structure described above, when a voltage with a negative potential is applied between the electrode 5 and the counter electrode 6, the positive ions (M ⁺ ) and electrons from the transparent conductive film 4 are injected into the electrode 5, and if the EC substance is tungsten oxide, tungsten bronze is formed and colored. Furthermore, when the polarity of the voltage is reversed, positive ions and electrons are extracted from the electrode 5 into the electrolytic solution 7 and the transparent conductive film 4, respectively, and the color is erased.

xM ⁺ +WO ₃ +xe ^- M ⁺ _x WO ₃ e ^- _x (1) (Decoloration) (Coloration) In this way, conventionally, coloring and decoloring were performed by applying a voltage between the electrode 5 and the counter electrode 6. However, the polarity of the applied voltage was different for coloring and decoloring, making it impossible to color and decolor at the same time. In other words, the response becomes slow. In addition, EC display devices use electrochemical reactions and are current-driven, so EC display devices use electric field-driven TN.
Although a liquid crystal display device inherently consumes a large amount of power, passing current separately in opposite directions for coloring and decoloring leads to an increase in power consumption. Furthermore, when a voltage is applied between the electrode 5 and the counter electrode 6, an increase in the area of the electrode to be colored leads to a decrease in response, and it is necessary to correct differences in coloring density caused by differences in response due to differences in temperature. , it is difficult to drive, which is a major problem in the practical application of EC display devices.

The present invention significantly improves these drawbacks and improves the EC
This makes it difficult to put the display device into practical use.

In the EC display device of the present invention, a part of the electrode is colored in advance to hold a charge, and a voltage is applied between the electrode holding a charge and the electrode not holding a charge. By transferring all the charge held by the electrode group to the latter electrode group,
The former electrode group is changed from a colored state to a decolored state, and the latter electrode group is changed from a decolored state to a colored state. Therefore, coloring and decoloring are performed at the same time, the response is faster than in the past, and only the current due to charge transfer between the electrode groups flows, and the current is shared between coloring and decoloring. Power consumption is reduced. Furthermore, if all the charges held by the former electrode group are transferred to the latter electrode group, no current will flow and the total amount of charge held by all the electrodes will not change. Therefore, by arbitrarily selecting the areas of the former electrode group and the latter electrode group, an arbitrary charge density can be obtained, and a display with an arbitrary coloring density (intermediate color) can be easily obtained. In addition, as shown in Figures 2 and 3, the decrease in response due to the increase in electrode area has been significantly improved compared to conventional drives, and furthermore, the decrease in response due to temperature changes has been significantly improved. is also improved over conventional drive, and the amount of transferred charge does not fluctuate.
There is no need for temperature correction, making it easy to manufacture a drive circuit.

Hereinafter, the present invention will be explained in detail with reference to Examples.

Example A glass-coated ceramic substrate was used as the lower substrate 2, and an indium oxide conductive film 4 was provided on the surface of the ceramic substrate by electron beam evaporation, and an etching process was performed to obtain a transparent conductive film 4 in a desired shape. Next, an insulating film 8 of alumina oxide is coated on the lead part of the transparent conductive film 4 by vacuum evaporation, and tungsten oxide is coated on the display pixel part of the transparent conductive film 4 in a vacuum of 2×10 ^-6 Torr. At a temperature of 100°C, the deposition was performed obliquely at an angle of 50° from the normal direction of the substrate to speed up the response, and at a deposition rate of approximately 20 Å/sec.
An electrode 5 of EC material with a film thickness of 3000 Å is formed, and further,
Cover the Au-Cr counter electrode 6 with spatter,
A lower substrate 2 shown in FIG. 5 was obtained. The upper substrate 1 was made of concave glass, the upper substrate 1 and the spacer 3 were integrated, and a cell gap of 0.5 mm was provided. As the electrolytic solution 7 filled in the cell gap, a 1M propylene carbonate solution of lithium perchlorate was used to prolong the life.
Also, the area of the electrode 5 can be calculated from the graph of charge density vs. coloring density (reflectance) shown in FIG.
-b, 5-c, 5-d, 5-e, 5-f as 1,
1・2, 1・4, 2, 2・8, 4・7mm ² .
In the EC display cell of the present invention, a voltage of 1.5 V is applied between the counter electrode 6 and the electrode 5-a to make the electrode 5-a a negative potential, and the electrode 5-a has a reflectance of 40.
% is colored. Similarly, the reflectance of the electrode 5-g
40% colored.

Next, when a voltage of 1.5 V is applied between the lead terminals 9-a and 9-b with the lead terminal 9-b at a negative potential, the electrode 5-a loses color and the electrode 5-b has a reflectance. 45% colored. Lead terminals 9-a and 9-b,
9-b and 9-c, 9-c and 9-d, 9-d and 9-
When voltage is applied sequentially to e, 9-e and 9-f, 9-f and 9-a..., the electrodes 5-a, 5-b, 5-c,
The colored pixels move sequentially as 5-d, 5-e, 5-f, 5-a..., and the coloring density of electrodes 5-a, 5-b... is 40%, 45%, 50%, 60%, It became 70% and 80%. Here, if the colored pixels are moved in units of 10 seconds, the bubbles emitted from the electrode 5-g (fish) will move upward every 10 seconds, gradually increasing in size and increasing the density. A gradually fading display was obtained. When the EC display device of the present invention was combined with a liquid crystal display device, a novel clock as shown in FIG. 6 was obtained in which hours and minutes were displayed using a liquid crystal display, and seconds were displayed using an EC display.

Furthermore, if the area of the electrode 5 is 1, 2, 3 mm ² and it is colored between the electrode 5 and the counter electrode 6, the electrode area is 1, 2, 3 mm 2.
The relationship between voltage application time of 3 mm ² and coloring density is shown in Figure 2, which clearly shows display area dependence (electrode areas 1, 2, and 3 mm ² correspond to a, b, and c, respectively). . However, when a voltage is applied between the colored electrode and the uncolored electrode, as shown in Figure 3 (the electrode areas 1, 2, and 3 mm ² are d, e, and f, respectively),
) There is clearly no display area dependence. In this way, in the present invention, even if the electrode area is changed,
There is no need to change the applied voltage and pulse width, a constant applied voltage pulse is sufficient, and a neutral color display can be easily obtained by arbitrarily selecting the electrode area from the graph shown in FIG.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a conventional EC display device;
The figure is a graph of voltage application time vs. reflectance showing the display electrode area dependence in the conventional EC driving method. Figure 3 is the voltage application time vs. reflectance graph showing the display electrode area dependence in the EC driving method of the present invention. Graph, FIG. 4 is a charge density-reflectance graph, FIG. 5 is a plan view showing an example of the electrode configuration of the present invention, and FIG. 6 is a three-dimensional view showing an example of the application of the present invention. . 1... Upper substrate, 2... Lower substrate, 3... Spacer, 4...
Transparent conductive film, 5... Electrode, 6... Counter electrode, 7... Electrolyte, 8... Insulating film, 9... Lead terminal, 5-a to 5-
g... Electrode, 9-a to 9-g... Lead terminal.

Claims (1)

[Claims] 1 An electrolyte is sandwiched between a pair of substrates, at least one of which is transparent, and a plurality of electrodes of an electrochemical color-forming substance are formed on a conductive film provided on at least one of the substrates, and the plurality of electrodes are formed on a conductive film provided on at least one of the substrates. In an electrochromic display device in which some of the electrodes constitute display pixels, a certain amount of charge is injected into and held in some of the electrodes to color them, and then the certain amount of electric charge is colored. When a voltage is applied between an electrode holding a charge and another electrode, and the charge held by the former is transferred to the latter to change the display, the area of the former and the area of the latter can be changed. 1. An electrochromic display device characterized by displaying intermediate colors by changing the charge density of charges held by electrodes.