JPS62204239A - Production of electrochromic display element - Google Patents

Abstract

PURPOSE:To enable decoloring of the titled element by means of a shortcircuit driving system by forming a tungsten oxide coating film on a substrate by specific deposition means, using a specific counter electrode substance composed of an active carbon fiber and a specific electrolyte. CONSTITUTION:The titled element comprises a pair of substrates 1 and 2 which are transparent in at least the display side, a display electrode member 4 formed the electrochromic substance layer 4b made of tungsten oxide via the display electrode 4a on the inside of the display side substrate 1, and a counter electrode member 6 formed the counter electrode substance layer 6b composed of the active carbon fiber via the counter electrode 6a on the inside surface of the counter substrate 2. An electrolyte 10 dissolved lithium perchlorate in propylene carbonate is enclosed between the both electrode members 4 and 6. The electrochromic substance layer 4b is formed by vapor depositing tungsten oxide as a vaporing source on the display electrode in the oxygen atmosphere under a partial pressure of oxygen gas of >=5X10<-4> Torr. Thus, the decoloring of the titled element enables by means of the shortcircuit driving system.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrochromic display element used in various displays using tungsten oxide as an electrochromic substance.

[Conventional technology]

As a typical display element of this type, an electrochromic material layer is formed on the inner surface of one of a pair of light-transmitting substrates via a display electrode made of a transparent electrode film, and the layer is divided into segments constituting a desired pattern. There is a display electrode in which a counter electrode material layer is provided on the inner surface of the other substrate via a counter electrode to serve as a counter electrode, and an electrolytic solution is sealed between the two electrodes of side substrates disposed opposite to each other. This is a display in which a voltage is applied to the display electrodes corresponding to the required segments using the above-mentioned counter electrode as a common electrode, and the color change of the reactant material via the electrolyte between the electrochromic material and the counter electrode material is used to display the display. It is.

As the electrochromic material, tungsten oxide is generally used for blue display. The color change in this case is based on the following reaction when, for example, a lithium salt dissolved in a non-aqueous solvent is used as the electrolyte.

By the way, as a conventional voltage driving method for carrying out the above reaction, a method is generally used in which a positive and negative bipolar power source is used to apply voltages of opposite polarity during coloring and decoloring. However, this method is not necessarily practical in that it requires the above-mentioned expensive power source, and voltage must also be applied during erasing.

Therefore, using a general unipolar power supply, voltage is applied only when displaying color, and when decoloring, a short circuit is made between the display electrode and the opposite electrode to erase the color. (Reference unknown)

[Problem that the invention seeks to solve]

However, the method of decoloring using the short-circuit drive method described above requires that the potentials of the display electrode side and the opposite electrode side be adjusted to an appropriate range in order to enable the above-mentioned decolorization. If the potential on the pole side is too high and the voltage that starts coloring/decoloring, that is, the threshold voltage, shifts to the positive side (oxidation side), even if a short circuit is made for decoloring, the color cannot be completely decolored by a minute current. The disadvantage is that there is no such thing. For this reason, if the counter electrode material on the counter electrode side is composed of an active material such as carbon black, manganese dioxide, or iron tungstate, and a binder, the type and mixing ratio of the above active materials must be adjusted. A countermeasure is taken to increase the potential of , thereby shifting the threshold voltage to the negative side (reduction side) as much as possible.

However, when activated carbon fiber is used as a counter electrode material, which can contribute to an increase in the amount of injected electricity and an improvement in the response characteristics of colored display compared to the counter electrode materials described above, in other words, when activated carbon fiber cloth is used as a counter electrode material, it is difficult to use activated carbon fiber cloth with carbon paste. When tungsten oxide is used as an electrochromic material to form a counter electrode material, the potential cannot be adjusted as described above.For this reason, when tungsten oxide is used as an electrochromic material, The potential becomes higher than that of the opposite polarity, and the threshold voltage shifts to the positive side, making it difficult to completely erase the color using the short-circuit drive method.

Therefore, this invention adjusts the potential on the display electrode side instead of adjusting the potential on the counter electrode side when tungsten oxide is used as an electrochromic material and activated carbon fiber, which contributes to improving response characteristics, is used as a counter electrode material. The object of the present invention is to shift the threshold voltage to the negative side, thereby obtaining an electrochromic display element that can erase color using a short-circuit drive method.

c. Means for Solving Problems] As a result of intensive studies to achieve the above object, the inventors discovered that lithium perchlorate was added to propylene carbonate as an electrolyte to be interposed between the display electrode and the counter electrode. When using a specific electrolytic solution made by dissolving a This invention was completed after learning that the potential on the display electrode side using fibers could be lowered compared to the opposing electrode side, thereby shifting the threshold voltage to the negative side, making it possible to erase colors using the short-circuit drive method. reached.

That is, the present invention includes a pair of substrates whose display side is transparent, a display electrode formed by forming an electrochromic material layer made of tungsten oxide on the inner surface of the display side substrate via a display electrode, and a counter substrate. An electrolyte having a counter electrode formed by forming a counter electrode material layer made of activated carbon fiber on the inner surface of the electrode via a counter electrode, and an electrolytic solution made by dissolving lithium perchlorate in propylene carbonate sealed between these two electrodes. In the method for manufacturing a chromic display element, when forming the electrochromic material layer, tungsten oxide as an evaporation source is vacuum-deposited on the display electrode in an oxygen gas atmosphere with an oxygen gas partial pressure of 5 x 10 Torr or more. The present invention relates to a method of manufacturing an electrochromic display element, which is characterized by obtaining an electrochromic display element that can be erased by a short-circuit driving method.

[Structure and operation of the invention]

In this invention, as described above, activated carbon fiber is used as the counter electrode material, and an electrolyte prepared by dissolving lithium perchlorate in propylene carbonate is used, while a tungsten oxide film is formed as the electrochromic material layer. The most significant feature is that tungsten oxide as an evaporation source is vacuum-deposited on the display electrode in an oxygen gas atmosphere with an oxygen gas partial pressure of 5×10 −4 Torr or more.

That is, when activated carbon fiber is used as the counter electrode material and the above-described specific electrolyte is used, the amount of electricity injected into the element increases and good results are obtained in terms of response characteristics of color display, etc., but on the other hand, There is a problem in that the threshold voltage of the element shifts to the positive side, making it difficult to erase the color using the short-circuit drive method. However, when the specific counter electrode material and electrolyte are used and the tungsten oxide coating as the electrochromic material layer is formed under the specific conditions, the potential on the display electrode side decreases and the threshold voltage decreases. is shifted to the negative side, thereby achieving the effect that color erasure can be achieved using the short-circuit drive method.

Conventionally, it has been known to form a tungsten oxide film as an electrochromic material layer using a vacuum evaporation method. It is also well known to distribute oxygen gas and the like. but,
In particular, when performing vacuum evaporation under an oxygen gas atmosphere as in this invention, when the oxygen gas partial pressure is set as described above, in the combination of the specific counter electrode material and electrolyte, the short-circuit driving method is used. It was completely unknown that a color erasable electrochromic display element could be obtained.

As described above, in this invention, by employing the above-mentioned specific means, it is possible to obtain an electrochromic display element that not only has good response characteristics for colored display but also can be erased by a short-circuit drive method. This also has the advantage of avoiding inconveniences such as slight discoloration of the device during storage as a result of the threshold voltage shifting to the negative side.

Specifically, in the evaporation formation of the tungsten oxide film in this invention, an evaporation source made of tungsten oxide powder formed into a disk shape is placed in a evaporation chamber, a display electrode is formed on one side in advance, and a display electrode is formed on one side as required. The display side substrate with a pattern mask is set, and while maintaining the predetermined degree of vacuum inside the deposition chamber, oxygen gas is circulated.
This is carried out by heating and evaporating the evaporation source using an electron beam irradiation method or a counter heating method.

It is important that the partial pressure of oxygen gas at this time is set to be 5X10-4 Torr or higher.If the partial pressure is lower than the above, that is, if the amount of oxygen gas is decreased, it will be difficult to shift the threshold voltage to the negative side. Therefore, erasing color using the short-circuit drive method becomes difficult. Note that if the partial pressure of oxygen gas becomes too large, that is, if the amount of oxygen gas is too large, the tungsten oxide film formed by vapor deposition becomes porous and its film strength decreases.
Generally, it is desirable to set it to 10XIO-4 Torr.

Furthermore, other gases such as nitrogen gas and argon gas may be allowed to flow together with the above-mentioned oxygen gas in the vapor deposition chamber as needed. Even in this case, the partial pressure of oxygen gas is set within the above range.

The deposition rate can be appropriately set depending on whether an electron beam irradiation method or a resistance heating method is employed. For example, in the case of an electron beam irradiation method, it is usually about 1 to 10 people/second. In addition, by heating the display side substrate during vapor deposition, favorable results can be obtained in terms of improving the adhesion of the vapor-deposited film, so the substrate is generally heated to a temperature of 60°C or higher, preferably up to 140°C. It is preferable to leave it there.

The thickness of the electrochromic material layer consisting of the tungsten oxide film formed in this way is usually 2,000 mm.
Approximately 0 to 20,000 people. If the thickness becomes too thin, problems such as a decrease in strength and lack of uniformity occur, and if it becomes too thick, problems such as increased electrical resistance occur, and in either case, favorable results in terms of display characteristics cannot be obtained.

The drawings show an example of the structure of an electrochromic display element manufactured by the method of this invention.

In the figure, 1 is a display side substrate made of a light-transmitting material such as glass, 2 is a counter-side substrate made of a similar light-transmitting material or non-light-transmitting material, and 3 is a peripheral area between the side substrates 1 and 2. A spacer 4 made of glass, polyester resin, or the like is interposed, and numeral 4 indicates a desired pattern consisting of a display electrode 4a and an electrochromic material layer 4b made of a vapor-deposited film of tungsten oxide formed thereon by the vapor-deposition method described above. The display electrode 5 is a protective film such as SiO that covers the exposed surface of the display electrode 4a.

Reference numeral 6 denotes a counter electrode composed of a counter electrode 6a and a counter electrode material layer 6b formed by bonding an activated carbon fiber cloth thereon with carbon paste; 7 a background provided between the counter electrode 2 and the display electrode 4; A material layer 8 is a lead terminal fixed to the side edge of the display substrate 1; 9 is a conductive layer formed of silver paste or the like to electrically connect the lead terminal 8 on the counter electrode side and the counter electrode 6a; 10 is an electrolytic solution made by dissolving lithium perchlorate in propylene carbonate sealed inside, and adding a small amount of water to this if necessary.

The display electrode 4a is made by vacuum-depositing a transparent conductive material such as indium oxide, tin oxide, or indium-tin composite oxide.
It is formed by adhering to the inner surface of the display side substrate 1 using existing thin film forming techniques such as sputtering and ion blating. Further, the counter electrode 6a is formed by applying a transparent conductive material in the same way as the display electrode 4a, or by compressing or adhering a foil-like material made of noble metals such as gold and platinum and alloys of these and other metals. It is adhered and formed on the inner surface of the opposing substrate 2. Furthermore, the background material layer 7 hides the counter electrode 6 and uses its own color tone as the background of the display, and is made of a sheet-shaped molded mixture of a pigment such as titanium dioxide and polytetrafluoroethylene powder. Alternatively, it can be formed by applying a gel body of pigment and electrolyte using a screen printing method or the like.

〔Effect of the invention〕

As described above, in the present invention, when using a specific counter electrode material made of activated carbon fibers and a specific electrolyte, a tungsten oxide film as an electromic material layer is formed by a specific vapor deposition method. By doing so, it is possible to obtain an electrochromic display element that can be decolored by a short-circuit driving method.

〔Example〕

Examples of the present invention will be described below in comparison with comparative examples.

Example 1 A predetermined pattern of display electrodes made of indium-tin composite oxide with a thickness of 2.500 mm and a thickness of 5.00 mm on one side
Display side substrate made of transparent glass (vertical 127fi, horizontal 127f
A photoresist is applied to the entire surface of the above-mentioned negative side (i. A mask was formed using the photoresist.

Next, the above display side substrate and a disk-shaped evaporation source made of a compression molded product of tungsten oxide powder with a diameter of 20 mm and a thickness of 10 mm are set in the chamber of a vacuum evaporation device, and the chamber is evacuated. After that, the partial pressure of oxygen gas was set to 5X10-4T.
Oxygen gas is circulated so that the substrate temperature is 12
The evaporation source was irradiated with an electron beam at an accelerating voltage of 6 KV at 0° C., and a tungsten oxide film with a thickness of 5,000 thick was formed by vapor deposition at an evaporation rate of 5 kV/sec. Thereafter, a portion other than the display pattern portion was removed by a lift-off method to obtain an electrochromic material layer in the display pattern, thereby forming a display electrode.

On the other hand, an opposing substrate made of transparent glass (length 127fi, width 127NM, thickness 1.5mm) on which a counter electrode made of indium-tin composite oxide with a thickness of 5,000 mm was previously formed on the - side.
A counter electrode was formed by bonding activated carbon fiber cloth (trade name: CH-20, manufactured by Kuraray Co., Ltd.) over the entire surface of the counter electrode with a sheet resistance of 1 m and a sheet resistance of 4 Ω/cal using carbon paste (trade name: PR-10, manufactured by Tokuriki Co., Ltd.). A material layer was formed to serve as 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, and the peripheral part is They were placed facing each other through a polyester resin annular spacer with a thickness of 500 μm and adhesively sealed, and 1% by weight of pure water was added to a propylene carbonate solution in which 1 mol/β lithium perchlorate was dissolved. Finally, lead terminals were attached and a conductive layer was formed by applying silver paste to produce an electrochromic display element having the structure shown in the drawing.

Example 2 An electrochromic display element was obtained in the same manner as in Example 1, except that the oxygen gas partial pressure when forming the tungsten oxide film by vapor deposition was set to 7×10 −4 Torr.

Example 3 An electrochromic display element was obtained in the same manner as in Example 1, except that the oxygen gas partial pressure when forming the tungsten oxide film by vapor deposition was set to IQXIO-4 Torr.

Comparative Example 1 An electrochromic display element was produced in the same manner as in Example 1, except that the oxygen gas partial pressure when forming the tungsten oxide film by vapor deposition was set to 3×10 −4 Torr.

Comparative Example 2 An electrochromic display element was obtained in the same manner as in Example 1, except that oxygen gas was not passed through the chamber during vapor deposition of the tungsten oxide film.

Each element according to the above Examples and Comparative Examples was colored and driven using a normal unipolar power source, and the threshold voltage at that time was measured. The results are as shown in the table below. In addition, after the coloring drive was performed using the above power source, the state when the display electrode side terminal and the counter electrode side terminal were short-circuited and the color was erased was investigated, and the results are also listed in the table below.

As is clear from the above results, according to the method of the present invention, it is possible to obtain an electrochromic display element in which the threshold voltage shifts to the negative side and can be completely erased even by a short-circuit drive method. I understand that.

[Brief explanation of drawings]

The drawing is a longitudinal sectional view showing an example of the structure of an electrochromic display element obtained by the method of the present invention.

Claims (1)

[Claims] (1) a pair of substrates whose display side is translucent;
A display electrode is formed by forming an electrochromic material layer made of tungsten oxide on the inner surface of the display side substrate via a display electrode, and a counter electrode material layer made of activated carbon fiber is formed on the inner surface of the opposing substrate via a counter electrode. In the method for manufacturing an electrochromic display element, the electrochromic display element has an electrolytic solution formed by dissolving lithium perchlorate in propylene carbonate sealed between the two electrodes. Oxygen gas partial pressure of tungsten oxide as a source is 5 × 10^-^
A method for manufacturing an electrochromic display element, characterized in that an electrochromic display element capable of erasing color by a short-circuit drive method is obtained by performing vacuum deposition on a display electrode in an oxygen gas atmosphere of 4 Torr or more.