JPH01213625A - Electrochromic display element - Google Patents

Abstract

PURPOSE:To prevent generation of bubbles in an element during storage and use by using specific composite metal oxide powder as a shielding material of a background material which shields a counter electrode. CONSTITUTION:The composite metal oxide powder to be used as the shielding material of the background material 10 consists of the composite metal oxide powder composed of titanium and at least one kind of the metal selected from zinc, nickel and antimony and is generally prepd. by subjecting the mixture composed of titanium oxide TiO2 powder, and the powder of at least one kind of the oxide selected from zinc oxide ZnO, nickel oxide NiO and antimony oxide Sb2O3 to high-temp. calcination in an oxygen atmosphere and grinding the calcined matter. This oxide does not exhibit a catalytic activity effect to the decomposition reaction of the propylene carbonate in an electrolyte 11. The bubbles are thereby hardly generated in the element and the excellent display grade and storage stability and the long life are obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrochromic display element used in various display devices.

[Conventional technology]

Various configurations of this type of display element are known to date, but one example is one in which an electrochromic material layer is provided on the inner surface of a light-transmitting display-side substrate via a transparent display electrode. A display electrode is divided into segments constituting a required pattern, and a counter electrode material layer is provided on the inner surface of the opposite substrate via a counter electrode to serve as a counter electrode, and a spacer is provided between the two electrodes of the side substrates facing each other. It is known that an electrolyte is sealed in the container.

In such a display element, by applying a voltage to the display electrodes corresponding to the required segments using the above-mentioned counter electrode as a common electrode, color change of the reactant through the electrolyte between the electrochromic substance and the counter electrode substance is performed. , the required display is made on the surface of the display side substrate. For example, in the case of a blue display, tungsten oxide (WO) is generally used as the electrochromic substance, but the color change in this case occurs when a lithium salt dissolved in a non-aqueous solvent is used as the electrolyte. , is based on the following reaction.

WO, +nL i” +ne-;=t, 1nWOs (transparent) (blue) By the way, as an electrolyte for such an electrochromic display element,
Generally, LiC is used in nonaqueous solvents such as propylene carbonate, γ-butyrolactone, dimethoxyethane, and dioxolane.
I Oa , LiP F & , L t B F 4
In addition to solutions in which lithium salts such as , L i As F 4 , and L s CFssOz are dissolved, solutions in which about 0.1 to 3 volume % of water is added as an electron donor are used. A method using propylene carbonate as the above-mentioned non-aqueous solvent is considered to be useful from the viewpoint of response characteristics (document unknown).

In addition, in this type of display element, because it is necessary to display the colored display clearly and with high contrast on the surface of the display side substrate, the counter electrode is usually hidden between the display electrode and the counter electrode, and the display element itself is A background material whose color tone is used as the background of the display is interposed. As the background material, a sheet formed by forming a mixture of titanium oxide powder as a hiding material and a binder such as polytetrafluoroethylene powder is widely used. (Reference unknown).

[Problem to be solved by the invention]

However, in conventional electrochromic display elements in which an electrolytic solution containing propylene carbonate as the main solvent and a background material using titanium oxide powder as a hiding material are sealed between both electrodes, air bubbles can form inside the element during storage or use. This tends to occur, which causes deterioration in display quality, and a high rate of element destruction, resulting in lower yields and shorter element life.

This invention was made in order to solve the above-mentioned conventional problems, and has excellent display quality and storage stability. The purpose is to provide a long-life electrochromic display element.

[Means to solve the problem]

In order to achieve the above object, the inventors first studied the cause of the generation of bubbles inside the conventional display element, and found that the bubbles are composed of carbon dioxide gas generated by the decomposition of propylene carbonate in the electrolytic solution. It has been found that titanium oxide, which is a concealing substance in the background material, has a high catalytic activity for the decomposition reaction of propylene carbonate.

After further intensive studies, we found that when a specific composite metal oxide powder was used as the above-mentioned concealing substance, the above-mentioned catalytic activity was significantly reduced, and the generation of bubbles due to the decomposition of propylene carbonate was greatly suppressed. The inventors have discovered that an electrochromic display element with excellent quality and storage stability and long life can be obtained, leading to the present invention.

That is, the present invention provides a display electrode formed on the inner surface of a translucent display side substrate and a counter electrode formed on the inner surface of the opposite side substrate, which hides the opposing electrode and displays its own color tone. In an electrochromic display element in which a background material and an electrolytic solution containing propylene carbonate are sealed, a concealing substance of the background material is selected from (a) titanium and (b) zinc, nickel, and antimony. The present invention relates to an electrochromic display element characterized by being made of powder of a composite metal oxide with at least one kind of metal.

[Structure and operation of the invention]

The composite metal oxide powder used as the concealing substance for the background material in this invention is, as described above, made of a composite metal oxide of (a) titanium and (b) at least one metal selected from zinc, nickel, and antimony. It exhibits almost no catalytic activity for the decomposition reaction of propylene carbonate in the electrolytic solution, and when used as the above-mentioned hiding material, it sufficiently hides the opposing electrode of the display element to reveal a white display background. It has the characteristic of being able to Therefore, in the electrochromic display element of the present invention using an electrolytic solution containing propylene carbonate and a background material containing the composite metal oxide powder as a hiding substance, carbon dioxide gas is not generated inside the element during storage or use. It is greatly suppressed and exhibits long life and excellent display quality.

The method for producing such composite metal oxide powder is not particularly limited and various methods can be adopted.
Nickel oxide (Nip), antimony oxide (Sbz03
A simple method is to sinter a mixture with a powder of at least one oxide selected from ) at a high temperature of about 500 to 2,000° C. in an oxygen atmosphere, and then pulverize the sintered product. In addition,
The above calcination uses a two-stage calcination method in which the material is fired at the above temperature for about 1 to 100 hours, then crushed, then pressure-molded into pellets, which are then fired again at the above temperature for about 1 to 100 hours and crushed. This is recommended from the viewpoint of sufficiently reducing the catalytic activity. The average particle diameter of the composite metal oxide powder thus produced is preferably set to about 0.2 to 3.0 μm.

The weight ratio of titanium (a) to metal fb) in the above composite metal oxide is (bl / (a) 0.5/100
A range of approximately 20/100 is preferable; if the metal component (b) is too small, the catalytic activity will not be sufficiently reduced; on the other hand, if the metal component (b) is too large, the hiding power as a masking substance will be reduced. will be in short supply.

The background material in this invention may be in the form of simply dispersing the above composite metal oxide powder in an electrolytic solution, but
From the viewpoint of concealability, it is preferable to form a sheet-like molded product having a thickness of about 0.05 to 2.0 fl by binding the above-mentioned powder through a binder. Various synthetic resin components can be used as the binder, but polytetrafluoroethylene powder is particularly suitable, and a mixture of this powder and the composite metal oxide powder at a weight ratio of about 1/100 to 10015 is used. It may be formed into a sheet by roll rolling or the like.

Next, an example of the electrochromic display element of the present invention will be explained with reference to the drawings.

In the figure, reference numeral 1 denotes a light-transmitting display-side substrate, and an electrochromic material layer 3 made of a thin tungsten oxide film is provided on the inner surface of this substrate 1 via a transparent display electrode 2, forming segments constituting a required pattern. A divided display electrode 4 is formed. Reference numeral 5 denotes a counter substrate, and a counter electrode material layer 7 is provided on the inner surface of the substrate 5 via a counter electrode 6 to form a counter electrode 8. And the above side board 1.5
are arranged to face each other with a spacer 9 made of synthetic resin, glass, etc. interposed therebetween, and the background material 10 and electrolyte 11 described above are sealed inside the spacer 9, that is, between the two electrodes 4°8.

Although a light-transmitting material such as glass is generally used as the above-mentioned both-side substrates 1.5, the opposite-side substrate 5 may be non-light-transmitting. Further, the display electrode 2 is made of indium-
It is made of a transparent conductive material such as tin composite oxide (hereinafter referred to as ``To''), and is usually 1. It is formed to a thickness of about 000 to 3,000 people. Furthermore, the counter electrode 6 is made of gold.

Precious metals such as platinum, alloys of these metals with other metals, or materials similar to those for the display electrode 2 are used, and in addition to the same thin film forming techniques described above, in the case of metals, the opposing electrodes are formed by pressing or bonding foil-like materials. Usually 1 on the inner surface of the side board 5
,000 to 5,000 people in thickness.

A tungsten oxide (WO3) thin film constituting the electrochromic material layer 3 is formed on the display electrode 2 to a thickness of usually about 3,000 to 10,000 wafers by the same thin film forming technique as described above. The counter electrode material layer 7 may use an oxide material such as tungsten oxide or iron tungstate as a counter electrode material, or may use a carbon material such as carbon powder, carbon fiber, or activated carbon fiber. You can. The latter carbon material has a high amount of injected electricity and excellent response characteristics.

In the case of carbon powder, the counter electrode material layer 7 containing such a carbon material can be formed by applying a paint containing the carbon powder and a binder resin onto the counter electrode 6 by screen printing or the like, and drying and curing the coating. In the case of carbon fibers and activated carbon fibers, these cross-like materials are connected to the counter electrode 6 via a conductive adhesive containing conductive particles such as carbon powder.
This is done by pasting it on top. Note that the counter electrode material layer 7 containing carbon powder or the conductive adhesive layer may contain powder of an oxide counter electrode active material such as tungsten oxide or iron tungstate.

When using carbon fiber or activated carbon fiber cloth, the thickness of the cloth must be 200 to 800 mm.
When carbon powder is used as the carbon material, the thickness of the counter electrode material layer formed by binding the powder with a binder is preferably about 20 to 500 μm.

The electrolytic solution 11 is made of propylene carbonate, which is a non-aqueous solvent, and
1CIOa , L i PF6 , L 1BF4 , L
iAsF, LiCFs A solution in which a lithium salt such as SOa is dissolved, or 0 as an electron donor in this solution.
．． It is preferable to add water in an amount of about 1 to 3% by volume.
In some cases, other solvents such as γ-butyrolactone, dimethoxyethane, dioxolane, etc. may be used in combination with the above-mentioned propylene carbonate as the main solvent.

In addition, 12 and 13 are lead terminals on the display electrode side and the counter electrode side fixed to the side edge of the display side substrate 1, and 14 is a material such as conductive paste or metal foil that constitutes the external lead-out part of the counter electrode 6. 15 is an insulating layer made of SiO2 or the like for protecting the display electrode 2.

〔Effect of the invention〕

As described above, according to the present invention, in an electrolytic solution containing propylene carbonate, by using a specific composite metal oxide powder as a concealing substance for a background material that conceals a counter electrode, it is possible to replace conventional titanium oxide When a powder is used as a hiding material, the decomposition of propylene carbonate caused by the catalytic activity of the hiding material is significantly suppressed, and air bubbles are not generated inside the device during storage or use, thereby improving display quality and storage. An electrochromic display element with excellent stability and long life can be provided.

〔Example〕

Hereinafter, this invention will be specifically explained based on Examples.

Example 1 After thoroughly mixing 100 g of TiOt powder and 5 g of ZnO powder in a mortar, the mixture was fired at 1.500° C. for 5 hours in an oxygen atmosphere, and the fired product was pulverized in a ball mill. Subsequently, the obtained powder was molded into pellets at a pressure of 100 kg/c11, and the pellets were fired again at 1,500°C in an oxygen atmosphere for 20 hours, and the fired product was crushed in a ball mill. A titanium-zinc composite metal oxide powder having an average particle diameter of 2.5 μm was obtained.

Next, add 10 g of this composite metal oxide powder to 2 ml of ethanol.
0.5 ml of a 60% by weight aqueous suspension of polytetrafluoroethylene powder was added and mixed into this dispersion, the solid content was placed on the filtration side, washed with water, and then heated at 105°C for 50 minutes.
After drying for a while, it was rolled with a roller to a thickness of 0.3 m.
A background material was prepared by forming a sheet of m in size and cutting it into a predetermined size.

On the other hand, on one side of the display-side substrate, which is made of transparent glass measuring 40 squares in length, 120 squares in width, and 1.1 squares in thickness, an I.
A display electrode with a predetermined pattern made of TO and a thickness of 5 mm on this
．． An electrochromic material layer consisting of a tungsten oxide thin film of 1,000 yen was formed by a vacuum evaporation method to form a display electrode.

Also, vertical 3611. A layer of 5,000 mm thick is placed on the entire surface of the opposite substrate made of transparent glass with a width of 116 mm and a thickness of 1.1 mm.
A counter electrode made of human ITO is formed by vacuum evaporation method, and carbon resin ink (trade name R manufactured by Tokurikisha Co., Ltd.) is applied on top of this counter electrode.
P-10. Two 10. A conductive adhesive solution consisting of a mixture of a paste containing phenolic novolak resin and carbon particles) and propylene carbonate in a weight ratio of 5:1.5 was
Screen printing was performed to a thickness of μm, and an activated carbon fiber cloth (product name CH-20 manufactured by Kuraray Co., Ltd.) was pressed onto the screen at 200°C.
By heating for 4 hours, a counter electrode material layer was formed by adhering the activated carbon fiber cloth to the counter electrode via a conductive adhesive, thereby forming a counter electrode.

Then, the above-mentioned side substrate is placed in such a manner that the display electrode and the counter electrode face each other, and the background material prepared above is interposed between the two electrodes, and a rectangular annular shape made of polyester resin with a thickness of 0.8 mm is placed around the periphery. Electrolysis made by adding 1% by volume of pure water to a propylene carbonate solution in which 1 mol/1 LiClO4 is dissolved inside, which are arranged facing each other with a spacer interposed and tightly sealed with an epoxy resin adhesive. Approximately 3 ml of liquid was sealed.

Next, lead terminals were attached and a conductive layer was formed by applying silver paste, thereby producing an electrochromic display element having the configuration shown in the drawings.

Example 2 A titanium-nickel composite metal oxide powder with an average particle size of 0.5 μm was obtained in the same manner as in Example 1, except that 5 g of NiO powder was used instead of ZnO powder, and this powder was used in Example 1. A background material was produced in the same manner, and an electrocomic display element was produced in the same manner as in Example 1 using this background material.

Example 3 A titanium-antimony composite metal oxide powder with an average particle size of 0.3 μm was obtained in the same manner as in Example 1, except that 5 g of 5bzO3 powder was used instead of ZnO powder, and this powder was used in Example 1. A background material was produced in the same manner, and an electrochromic display element was produced in the same manner as in Example 1 using this background material.

Comparative example: average particle size 2 instead of titanium-zinc composite metal oxide powder
．． A background material was obtained in the same manner as in Example 1 using 5 μm titanium oxide powder, and an electrochromic display element was produced in the same manner as in Example 1 using this background material.

After storing 100 pieces of each of the electrochromic display elements of the above Examples and Comparative Examples at a temperature of 60'C for 100 days, the numbers of bubble-generating cells and broken cells were visually examined, and the results are shown in the table below. was gotten.

From the results in the table above, it can be seen that the electrochromic display elements of the present invention (Examples 1 to 3) using specific composite metal oxide powders containing titanium as the hiding material of the background material do not use ordinary titanium oxide powder as the hiding material. Compared to an electrochromic display element with a conventional structure (comparative example) that uses a background material of It is clear that

[Brief explanation of the drawing]

The drawing is a sectional view showing a structural example of an electrochromic display element according to the present invention. l...Display side substrate, 4...Display pole, 5...Counter side substrate, 8...Counter pole, 10...Background material, 11...
Electrolyte solution [: table attached 14M feet: 1) 5 Kairyu Rini 8: Kozo Ei 9 Ko 11: Denbutsu Ward

Claims (4)

[Claims] (1) Between the display electrode formed on the inner surface of the transparent display-side substrate and the counter electrode formed on the inner surface of the counter-side substrate, the counter electrode is hidden and its own color tone becomes the background of the display. In an electrochromic display element comprising a background material and an electrolytic solution containing propylene carbonate, the hiding material of the background material is (a) titanium and (b) at least one selected from zinc, nickel and antimony. An electrochromic display element comprising a powder of a composite metal oxide with a metal. (2) Weight ratio (b) of titanium in (a) and metal in (b)
The electrochromic display element according to claim 1, wherein /(a) is in the range of 0.5/100 to 20/100. (3) Claim (1) or (2) wherein the background material is a sheet-like molded product made by binding composite metal oxide powder through a binder.
).The electrochromic display element described in ). (4) The electrochromic display element according to claim (3), wherein the binder comprises polytetrafluoroethylene powder.