JPH0652355B2 - Electrochromic display element - Google Patents

Description

The present invention relates to an electrochromic display device. More specifically, the present invention relates to an electrochromic display element having a small difference in color density between the element end portion and the element center portion.

[Conventional technology]

As shown in FIG. 2, the counter electrode in the conventional electrochromic display element has an ITO film on a substrate 6a made of a glass plate for providing conductivity and preventing elution of harmful ions from the glass plate into the electrolyte. A conductive metal oxide film 6b such as (indium tin oxide film) or tin oxide film is formed, and the counter electrode material layer 8 is formed on the conductive metal oxide film 6b (for example, Japanese Patent Application No. 58-58). -193721 publication).

[Problems to be solved by the invention]

However, since the conductive metal oxide film 6b as described above is formed by vapor deposition, electrodeposition or the like, it is not possible to increase the film thickness, so that sufficient conductivity cannot be obtained, and the drive power source is not required. There has been a problem in that there is a difference in electrical resistance between the element end portion close to the input lead terminal and the element center portion far from the lead terminal, resulting in a difference in color density of the electrochromic substance.

Further, the conductive metal oxide film 6b is hard and has a uniform surface and is suitable for mounting lead terminals, but the contact with the opposite electrode material is not so dense, and the conductive metal oxide film is also conductive from this surface. And the amount of electricity injected into the entire display unit is reduced, which also promotes the occurrence of the difference in color density.

[Means for solving problems]

This invention solves the above-mentioned problems of the prior art by providing a conductive layer made of a mixture of a conductive substance and a binding resin on a conductive metal oxide film of a counter electrode substrate, and forming a conductive layer on the conductive layer. By forming a counter electrode material layer on the counter electrode, the conductivity on the counter electrode side is enhanced, the difference in color density between the element end portion and the element central portion is reduced, and the amount of electricity injected into the entire display portion is increased.

The conductive layer as described above is a conductive metal oxide film of a counter electrode substrate prepared by mixing a conductive substance and a binding resin in the presence of a solvent to a viscosity such that they can be applied, and adjusting a slurry or paste mixture. It is formed by coating on top and drying. The conductive layer formed by such coating is
Compared with the conductive metal oxide film such as ITO film or tin oxide film formed by vapor deposition, it has high conductivity, and the difference in electrical resistance between the element end portion and the element center portion is reduced to reduce As described above, it is possible to reduce the difference in color density between the end portion of the element and the central portion of the element and increase the amount of electricity injected into the entire display portion.

〔Example〕

 Next, the present invention will be described in more detail with reference to examples.

Example 1 An ITO film having a thickness of 300 nm was formed by vapor deposition as a conductive metal oxide film on a glass plate having a thickness of 1.1 mm, and the ITO film was used as a counter electrode substrate to prepare a conductive layer and a counter electrode as shown below. A material layer was formed.

Carbon resin ink, which is a commercially available conductive paint (carbon powder and epoxy thermosetting resin are mixed in the presence of a solvent, and the viscosity is adjusted to 500 voids), and propylene carbonate in a weight ratio of 100: 5. The mixed paste mixture was applied on the ITO film of the counter electrode substrate by a screen printing machine to a thickness of about 70 μm (however, during film formation).
The conductive layer was formed by heat treatment at 0 ° C. for 15 minutes. Next, iron tungstate, carbon resin ink (described above), and propylene carbonate were mixed in a weight ratio of 10 on the conductive layer.
A mixture of 0: 100: 40 was screened to a thickness of 0.
It was applied to 20 mm (at the time of film formation) and then heated at 200 ° C. for 4 hours to form a counter electrode material layer.

A counter electrode having a conductive layer manufactured as described above, and tungsten oxide (WO ₃ ) as an electrochromic substance
An electrochromic display device shown in FIG. 1 was prepared using a display electrode prepared by a conventional method and a liquid electrolyte prepared by dissolving 1 mol / liter of lithium perchlorate in propylene carbonate.

In FIG. 1, reference numeral 1 denotes a display electrode, which is a display electrode substrate 2 having a transparent conductive film 2b formed on a transparent glass plate 2a,
It has an electrochromic material layer 3 formed on the transparent conductive film 2b of the display electrode substrate 2. Then, a protective film 4 is provided on a portion of the transparent conductive film 2b inside the device where the electrochromic material layer 3 is not formed.
In this embodiment, the transparent conductive film 2b is made of an ITO film,
As described above, tungsten oxide is used as the electrochromic material, and the protective film 4 is a vapor deposition film of silicon dioxide.

Reference numeral 5 is a counter electrode. The counter electrode 5 is a counter electrode substrate 6 in which a conductive metal oxide film 6b of ITO is formed on a substrate 6a made of a glass plate as described above, and a conductive metal of the counter electrode substrate 6. It comprises a conductive layer 7 provided on the oxide film 6b and a counter electrode material layer 8 formed on the conductive layer 7.

9 is a liquid electrolyte, 1 mol / mol of lithium perchlorate is dissolved in propylene carbonate as described above, 10 is a background material, and this background material 10 is a porous polytetrafluoro with titanium dioxide powder dispersed and contained. An ethylene sheet is used. 11 is a polyester spacer,
The spacer 11 has a rectangular ring shape, and the upper and lower surfaces thereof are adhered to the peripheral edge of the display electrode substrate 2 and the peripheral electrode portion of the counter electrode substrate 6 with an adhesive agent. The liquid electrolyte 9 and the background material 10 described above are enclosed in the space formed by the counter electrode substrate 6.

Example 2 A ferritic stainless steel plate having a thickness of 0.3 mm (containing nickel, chromium, and molybdenum, the content of which was 5% by weight of nickel, was used as the counter electrode substrate instead of the glass plate.
An electrochromic display device was prepared in the same manner as in Example 1 except that chromium was 25% by weight and molybdenum was 1% by weight. Of course, an ITO film is formed on the ferritic stainless steel plate, a conductive layer is provided on the ITO film, and a counter electrode material layer is formed on the conductive layer.
ITO film thickness, conductive layer, counter electrode material layer material, thickness,
The forming method and the like are the same as those in the first embodiment.

Comparative Example An electrochromic display device was prepared in the same manner as in Example 1 except that the counter electrode material layer was directly formed on the ITO film of the counter electrode substrate in which ITO was vapor-deposited to a thickness of 300 nm on a glass plate having a thickness of 1.1 mm. It was made.

The electrochromic display device is as shown in FIG. 2, and the counter electrode material layer 8 is directly formed on the conductive metal oxide film 6b of ITO.

The following table shows the results of examining the difference in color density between the character at the element end and the character at the central portion of the electrochromic display elements of Examples 1 and 2 and the electrochromic display element of the comparative example. Each electrochromic display element has a size of 48 mm × 170 mm, and the display characters of the electrochromic material are 7 characters, and the color development area of the characters is about 2.5 cm ²
Is. Since the difference in color density between the character at the end of the device and the character at the center of the device can be evaluated numerically by the difference in the amount of electricity injected into those characters, the amount of electricity injected per character is shown in the table. The amount of electricity injected in the table is measured under the conditions of 20 ± 2 ° C., 1.65 V, and 1.0 second.

As shown in the above table, the electrochromic display elements of Examples 1 and 2 of the present invention are different from the electrochromic display element of the comparative example in the amount of injected electricity between the character at the end of the element and the character at the center of the element. It is clear that the difference is small and the difference in color density between those letters is small. Also, the amount of electricity injected is
The electrochromic display elements of Examples 1 and 2 of the present invention are larger than the electrochromic display element of the comparative example.

Although the conductive layer 7 is made of carbon as a conductive substance in the embodiment, it may be made of a metal such as nickel as a conductive substance.

As for the conductive layer 7, as illustrated in the examples, the conductive substance and the binder resin are mixed and adjusted to have a viscosity such that they can be applied in the presence of a solvent, and a slurry-like or paste-like mixture is screen-printed or spray-coated. It is formed by applying with an appropriate applying means such as brush coating and drying. Since the larger the film thickness is, the more the conductivity is improved, the thickness is set to 70 μm in the embodiment, but it is normally about 40 μm or more.

Further, although tungsten oxide was used as the electrochromic substance of the display electrode in the examples, instead of it, for example, iron hexacyanoferrate (Prussian blue), iron pentacyanocarbonylferrate, iron hexacyanoruthenate (ruthenium purple), hexacyano A cyano complex of a transition metal such as iron osmate (osmium purple) or iron hexacyanomanganate may be used. Also,
Depending on the type of electrochromic substance, the electrolyte may be an aqueous one instead of the organic one used in the examples.

Although iron tungstate was used as the counter electrode material in the examples, for example, activated carbon fiber, manganese dioxide or the like may be used instead.

〔The invention's effect〕

As described above, according to the present invention, by providing the conductive layer on the conductive metal oxide film of the counter electrode substrate, the conductivity on the counter electrode side is improved and the difference in color density between characters is reduced. At the same time, the amount of electricity injected into the entire display section was improved.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the electrochromic display element of the present invention, and FIG. 2 is a sectional view showing a conventional electrochromic display element. 1 ... Display electrode, 5 ... Counter electrode, 6 ... Counter electrode substrate, 6b ... Conductive metal oxide film, 7 ... Conductive layer, 8 ... Counter electrode material layer, 9 ... Electrolyte

Claims (3)

[Claims] 1. A conductive metal oxide film 6b of a counter electrode substrate 6 of the counter electrode 5 having a display electrode 1, an electrolyte 9 and a counter electrode 5,
An electrochromic display element, characterized in that a conductive layer 7 made of a mixture of a conductive material and a resin is provided between the counter electrode material layer 8. 2. The electrochromic display element according to claim 1, wherein the conductive substance of the conductive layer 7 is carbon. 3. The electrochromic display device according to claim 1, wherein the conductive metal oxide film 6b is an ITO film or a tin oxide film.