JPS6315231A - Electrochromic display element - Google Patents

Abstract

PURPOSE:To considerably simplify a production process by constituting a transparent electrode layer of a display electrode of a thin indium-tin compound oxide film (ITO film) having a specific etching characteristic. CONSTITUTION:Tungsten oxide is used as an electrochromic material 3, activated carbon fibers are used as a counter electrode material 7 and a PC-LiClO4-H2 O electrolytic soln. is used as an electrolytic soln. 9. The transparent electrode layer 2 is constituted of the ITO film which consists of a hydrochloric acid-nitric acid soln. mixture composed of HCl:HNO3:H2O at 50:8:42 volumetric ratio and has <=450Angstrom /min, more preferably about 300-400Angstrom /min etching rate at 45 deg.C. The electric decomposition is, therefore, hardly generated and the dissolution of the transparent electrode layer 2 in the electrolytic soln. 9 and the deterioration thereof are prevented even if said electrode layer is in a contact state with the electrolytic soln. 9. The formation of the conventional insulating protective film is thereby omitted and the considerable simplification and manpower saving of the production process as well as the shortened time and reduced cost thereof are attained.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to an electrochromic display element that performs display on various display devices by utilizing color change caused by an electrochemical reaction of an electrochromic substance made of tungsten oxide. .

[Prior Art] In general, an electrochromic display element, as shown in FIG. 2, includes an electrochromic substance 3 provided on the inner surface of a transparent display substrate 1 via a transparent electrode layer 2 to form a desired pattern. A display electrode 4 is divided into segments constituting a display electrode 4, a counter electrode material 7 is provided on the inner surface of the opposite substrate 5 via an electrode layer 6 to form a counter electrode 8, and the side substrates 1 and 5 are used as both electrodes 4.
, 8 are arranged facing each other, and an electrolytic solution 9 is sealed between the electrodes 4 and 8. In addition, 10 is a spacer interposed between the peripheral parts of the side substrate 1.5, and 11 is a display electrode 4.
12 is a lead terminal, and 13 is a conductive layer that electrically connects the electrode layer 6 and the lead terminal 12 on the opposing side.

In the display element having the above configuration, by applying a voltage to the required display electrodes 4 using the counter electrode 8 as a common electrode, coloring changes due to a reaction between the electrochromic substance 3 and the counter electrode substance 7 via the electrolyte 9, The required pattern is displayed. This color change is expressed by the following equation when, for example, the electrochromic material 3 is tungsten oxide and the electrolyte 9 is a lithium salt.

WO3+ nL+ + ne, LinWO3(
(transparent) (blue) By the way, the performance of this type of display element, such as the amount of electricity injected and the response characteristics, is greatly influenced by the type of counter electrode material 7 and electrolyte 9 used depending on the electrochromic material 3, and these The driving conditions are also almost determined by the combination of. Therefore, various combinations of these have been studied in the past, but among them, when the electrochromic material 3 is tungsten oxide, which is the most widely used, activated carbon fiber is used as the counter electrode material 7, and propylene carbonate-permeate is used as the electrolyte. Lithium chlorate-water system (
Display elements using an electrolyte (hereinafter referred to as P C-Li ClO4-H2O system) are known to have a high amount of injected electricity and excellent response characteristics, and this is usually ±1.3.
It is driven by applying a square wave voltage of less than v and less than 0.6 seconds.

[Problem that the invention seeks to solve]

However, as described above, in the conventional display element in which the electrochromic substance 3 is tungsten oxide, the counter electrode material 7 made of activated carbon fiber, and the PC-Li ClO4-H2O electrolyte 9, the display electrode When the indium-tin composite oxide thin film (hereinafter referred to as ITO film) commonly used as the transparent electrode layer 2 in No. 4 comes into contact with the electrolytic solution 9, electrolysis occurs and it dissolves in the electrolytic solution. To avoid this, it is necessary to cover the surface portion of the transparent electrode layer 2 that is not covered with the electrochromic material 3 with an insulating protective film 14 made of SiO□, etc., as shown in FIG. there were.

Therefore, when manufacturing the above-mentioned conventional display element,
A very complicated process is required to form the insulating protective film 14 by vapor deposition and patterning by etching.
There is a problem that a great deal of labor and time is required, and the cost is high.

[Means for solving problems]

As a result of intensive studies to solve the above-mentioned conventional problems, the inventors discovered that the electrochromic material is tungsten oxide, a counter electrode material made of activated carbon fiber, and PC-Li.
In a display element using a CrO, -H20-based electrolyte,
When a specific ITO film is used as the transparent electrode layer of the display electrode, even if the ITO film comes into contact with an electrolyte during operation, it is unlikely to deteriorate due to electrolysis, and the cycle life will not be shortened. The inventors have discovered that it is possible to omit the formation of an insulating protective film to greatly simplify the manufacturing process, thereby saving labor, time, and cost, and have come up with this invention.

That is, in the present invention, a pair of substrates whose at least the display side is translucent are disposed facing each other, and a display electrode is formed by providing an electrochromic substance made of tungsten oxide on the inner surface of the display side substrate via a transparent electrode layer. , an electrochromic display element in which a counter electrode is formed by providing a counter electrode material on the inner surface of a counter substrate via an electrode layer, and an electrolytic solution is sealed between the two electrodes, wherein the counter electrode material is made of activated carbon fiber. , the electrolyte is PC-LiCeO.

-H20-based electrolyte, and the transparent electrode layer has a volume ratio of HCl:HNO3:H2O of 50:8:
The present invention relates to an electrochromic display element characterized in that an ITO film having an etching rate of 450 Å/min or less at 45° C. with a hydrochloric acid-nitric acid mixture of No. 42 is used.

(Structure and operation of the invention) FIG. 1 shows an example of the structure of an electrochromic display element according to the present invention, and each component in the figure is the same as the component with the same reference numeral in the conventional structure shown in FIG. However, compared to the conventional structure described above, the surface portion of the transparent electrode layer 2 that is not covered with the electrochromic substance 3 is not covered with the insulating protective film (14 in FIG. 2) and is in contact with the electrolyte 9. They are different in some respects.

That is, the display element of the present invention uses tungsten oxide as the electrochromic material 3, activated carbon fiber as the counter electrode material 7, and PC-LiClO4- as the electrolyte 9.
It has the advantage that the amount of electricity injected is large and the response characteristics are excellent by using an H2O-based electrolyte, and it is driven by applying a square wave voltage of ±1.3 V or less and 0.6 seconds or less. , the transparent electrode layer 2 is HCl:HNO3:Hi! as described above. The volume ratio of 0 is 50:8:
The etching rate at 45°C with a hydrochloric acid-nitric acid mixture of No. 42 is 45 OA/min or less, particularly preferably 300 to 400 OA/min.
Since it is made of an ITO film with a thickness of about Å/min, even if the transparent electrode layer 2 is in contact with the electrolytic solution 9 during driving, it is difficult to cause electrolytic decomposition, and as a result, it dissolves in the electrolytic solution 9 and deteriorates. This will be prevented.

The reason for this is not clear, but while the etching rate of the ITO film used for the transparent electrode layer 2 of conventional display elements of this type is generally about 600 to 700^/min, the etching rate of the present invention is not clear. The above-mentioned ITO film of the display element has a characteristic that the etching rate is very low, so the film has extremely high density and has high electrochemical stability with respect to the above-mentioned specific electrolyte even under driving voltage. It is assumed that.

To form the ITO film having the above-mentioned etching characteristics in this invention, it is possible to employ various existing thin film forming methods such as various vacuum evaporation methods and spackling methods that form films under high vacuum, and depending on the method used, the substrate may be Although various conditions such as temperature, film formation rate, degree of vacuum, etc. may be selected as appropriate, electron beam evaporation is particularly suitable.

When employing the above electron beam evaporation method, the etching characteristics of the ITO film formed vary depending on the combination of various conditions, but usually the substrate temperature is set to a relatively high temperature of about 400 to 500°C, and the film formation rate is set to 60°C. It is desirable that the evaporation rate is relatively small, about 120λ/min, and ITO is used as the evaporation source, and the degree of vacuum is 1×10 to 5×10 To
It is preferable to set it to about rr.

As mentioned above, the ITO film thus formed has a processing speed of 450^/cm at 45°C using the hydrochloric acid-nitric acid mixture.
The etching rate should be less than 300 Å/min, preferably about 300 to 400 Å/min; however, if the etching rate is higher than gO^/min, drive deterioration will occur and the cycle life of the display element will be shortened; If it is too small, etching for patterning the transparent electrode layer becomes difficult.

The thickness of the transparent electrode layer 2 made of the above-mentioned ITO film is 2,
It is preferable to set it to about 000 to 2,500λ.

Electrochromic material made of tungsten oxide 3
After patterning the transparent electrode layer 2 made of the above-mentioned ITO film on the inner surface of the display side substrate 1, various vacuum evaporation methods such as electron beam evaporation, sputtering, ion blating, etc. are applied onto the transparent electrode layer 2. The required pattern is formed using the existing thin film forming method of about 3,000 to 7,000 OOA.

The electrode layer 6 of the counter electrode 8 is formed by depositing an ITO film similar to the transparent electrode layer 2 of the display electrode 4 or a conventional ITO film using various thin film forming methods, or by depositing a foil-like material made of gold, platinum, etc. is formed on the inner surface of the opposing substrate 5 by pressure bonding or adhesion.

The counter electrode material 7 is made of activated carbon fiber as described above,
Usually, it is formed by pasting a cloth with a thickness of about 400 to 1,000 p on the electrode layer 6 using carbon paste.

The electrolyte 9 is PC-L 1CIO, -H2O as described above.
When the electrochromic material 3 is made of tungsten oxide, the combination of this electrolytic solution 9 and the counter electrode material 7 made of activated carbon fibers provides a display element with a large amount of injected electricity and excellent response characteristics. The specific composition of this electrolytic solution 9 is that H
It is preferable to add about 0.3 to 1% by volume of 2O.

The background material 11 hides the counter electrode 8 and uses its own color tone as the background of the display, and is made by placing a sheet-shaped molded mixture of a pigment such as titanium dioxide and polytetrafluoroethylene powder on the counter electrode 8. It can be formed by pasting or by applying a gel of pigment and electrolyte using screen printing or the like.

Furthermore, a light-transmitting material such as glass is used as the display-side substrate 1, and a similar light-transmitting material or a non-light-transmitting material is used as the opposite-side substrate 5. Glass or polyester resin is used for the spacer 10, and silver paste is used for the conductive W1 layer 13.

〔Effect of the invention〕

In the electrochromic display element according to the present invention, the electrochromic material is made of tungsten oxide, and the counter electrode material is made of activated carbon fiber and PC-L 1ClO.
In devices that use a 4-H,O-based electrolyte, the transparent electrode layer of the display electrode is composed of an ITO film with specific etching characteristics. Resistant to deterioration even when in contact with
This prevents the cycle life from decreasing due to this deterioration.
There is no need for an insulating protective film to cover the exposed surface of the transparent electrode layer as in conventional display elements of this type, and when manufacturing the element,
The complicated process for vapor deposition and patterning of the above-mentioned insulating protective film can be omitted, which greatly simplifies the process and thereby saves labor, time, and costs. It has the advantage that the amount of electricity injected is large based on the combination of liquids and the response characteristics are excellent.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail.

Note that the display-side ITO substrates A to D used in each example and comparative example have a length of 127 am and a width of 127 m.

On the surface of a substrate made of a glass plate with a thickness of 1.1 mm, using an indium-tin composite oxide as an evaporation source by electron beam evaporation, at a vacuum degree of 3 x 10 Torr,
A thickness of 2.500A was obtained by variously adjusting the substrate temperature and film formation rate.
An ITO film was formed to form a transparent electrode layer. The transparent electrode layer of each ITO substrate was HC/ :HNO3:H2O
The etching rate when etching was performed with a hydrochloric acid-nitric acid mixture at 45 DEG C. in a volume ratio of 50:8:42 is shown in Table 1 below.

Table 1 Example 1 After forming the transparent electrode layer of the display-side ITO substrate A into a predetermined pattern by photo-etching, tungsten oxide was deposited on the transparent electrode layer using an electron beam evaporation method using a mask to a thickness of 5.
An electrochromic material layer with a predetermined pattern of 0OOA was formed to serve as a display electrode.

On the other hand, the thickness is 4. An activated carbon fiber cloth with a thickness of 0.5B (
Carbon paste (product name: CH-20) manufactured by Kuraray Co., Ltd.
A counter electrode material layer was formed by bonding the entire surface together using a product (trade name: PR-10, manufactured by Taikisha) to form a counter electrode.

Then, the above-mentioned side substrate is arranged such that the display electrode and the counter electrode face each other, and a background material made of a sheet-shaped molded mixture of titanium dioxide pigment and polytetrafluoroethylene powder is interposed between the two electrodes. They were placed facing each other with a 500 mm annular spacer made of polyester resin and sealed with adhesive, and 1% by volume of pure water was added to a propylene carbonate solution in which 1 mole of lithium perchlorate was dissolved. Finally, lead terminals are attached and a conductive layer is formed by applying silver paste.
An electrochromic display element having the configuration shown in FIG. 1 was manufactured.

Example 2 An electrochromic display element was produced in the same manner as in Example 1 except that display side ITO substrate A was replaced with B.

Comparative Example 1 An electrochromic display element was prepared in the same manner as in Example 1 except that C was used instead of the display side ITO substrate A.

Comparative Example 2 An electrochromic display element was produced in the same manner as in Example 1, except that display side ITO substrate A was replaced with D.

For each of the display elements of the above Examples and Comparative Examples, a square wave voltage of ±1.2V for 0.6 seconds was applied between the display electrode and the opposite electrode, and repeated driving was performed to repeat color development and disappearance. The amount of electricity injected after driving 1 million times was measured. In addition, the above driving was continued and the number of driving times until visible dissolution was observed in the ITO film constituting the transparent electrode layer of the display electrode was measured, and the display element was disassembled after 1.5 million times of driving and the ITO film was removed. The actual thickness of the membrane was measured. These results are shown in Table 2. The presence or absence of the above-mentioned dissolution was determined by comparing the color of the ITO film of the driven segment with the color of the ITO film of the non-driven segment, and whether or not a color change due to dissolution was discernible with the naked eye.

Table 2 From the results in Table 2 above, the display element of the present invention (Examples 1 and 2) in which the transparent electrode layer of the display electrode is made of an ITO film whose etching rate with the hydrochloric acid-nitric acid mixture is 450 A/min or less
It is clear that even if the number of times of driving becomes very large, the ITO film is unlikely to dissolve, the amount of electricity injected is high, and the cycle life is excellent. On the other hand, in display elements (Comparative Examples 1 and 2) in which the transparent electrode layer of the display electrode is made of an ITO film that is higher than the etching rate, the ITO film dissolves when the number of drives reaches a certain level, and the number of drives increases further. As the amount increases, the dissolution becomes significant and the amount of electricity injected also decreases.
It can be seen that the cycle life is inferior.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing an example of the structure of an electrochromic display element according to the present invention, and FIG. 2 is a longitudinal sectional view showing an example of the structure of a conventional electrochromic display element. DESCRIPTION OF SYMBOLS 1... Display side substrate, 2... Transparent electrode layer, 3... Electrochromic substance, 4... Display electrode, 5... Opposite side substrate, 6... Electrode layer, 7... Counterpole material, 8...
・Counter electrode, 9... Electrolyte patent applicant Hitachi Maxell Ltd. Figure 1m Figure 2m

Claims (1)

[Claims] (1) A pair of substrates whose display sides are translucent are arranged opposite each other, a display electrode is formed by providing an electrochromic substance made of tungsten oxide on the inner surface of the display side substrates via a transparent electrode layer, and In an electrochromic display element in which a counter electrode is formed by providing a counter electrode material on the inner surface of a substrate through an electrode layer, and an electrolytic solution is sealed between the two electrodes, the counter electrode material is made of activated carbon fiber, The liquid is composed of a propylene carbonate-lithium perchlorate-aqueous electrolyte, and the transparent electrode layer has a volume ratio of HCl:HNO_3:H_2O of 50:8:
1. An electrochromic display element characterized in that an indium-tin composite oxide thin film having an etching rate of 450 Å/min or less at 45° C. with a hydrochloric acid-nitric acid mixture of No. 42 is used.