JPH0140967B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to electrochromic display elements, and particularly to high contrast electrochromic display elements.

Conventional electrochromic display elements include a pair of electrode layers, only one of which is translucent, with a coloring layer made of a transition metal oxide, such as a tungsten oxide layer, and an electrolyte layer interposed between the electrode layers, or a pair of electrode layers, one of which is translucent. An electrolyte is sandwiched between transparent electrodes,
A first layer consisting of a layer of metal oxide, such as tungsten oxide, which develops color in a reduced state on the surface of one electrode.
on the surface of the other electrode, a metal oxide that develops color in the oxidized state, e.g.
A device comprising a second electrochromic layer made of Cr ₂ O ₃ , nickel oxide, etc. is known (Japanese Patent Laid-Open No. 55-64216).

However, in the case of such conventional electrochromic display elements, in the first type of electrochromic display element, the coloring layer is visible only from the transparent electrode side, so the range of use is narrow, and In the electrochromic display element of type 2, since the coloring intensity of the second electrochromic layer is weak, the coloring intensity is almost equal to the coloring intensity of the first electrochromic layer, so the coloring intensity is low. However, there was a problem with low contrast. In addition, in these elements, the concentration of coloring species can be increased by performing more electrolysis, but in this case, there are problems such as deterioration of electrolysis due to gas generation, accumulation of colored species, and shortened lifespan. The dot was hot.

The present invention has been made by focusing on such conventional problems, and includes a first electrochromic layer on the surface of one of a pair of electrodes, at least one of which is translucent, and a first electrochromic layer on the surface of the opposing electrode. In an electrochromic display element comprising a second electrochromic layer thereon and an electrolyte sealed between both electrodes, the first electrochromic layer is composed of a metal oxide layer that develops color in a reduced state; The second electrochromic layer has the following general formula: M _1x [M ₂ (CN) ₆ ] y (1) where M ₁ and M ₂ are transition metals, x is 3-4,
y represents 2 to 3).

The metal oxide of the metal oxide layer that forms the first electrochromic layer used in the display element of the present invention is preferably a transition metal oxide, such as WO ₃ , MoO ₃ , Nb ₂ O, etc. ₅ , _{Cr2O3 ,}
Examples include Ta ₂ O ₅ and TiO ₂ .

In addition, as for the transition metal mixed valence complex represented by the above formula (1) constituting the second electrochromic layer, M ₁ is iron (Fe), copper (Cu), chromium (Cr),
Compounds in which M ₂ is iron (Fe), ruthenium (Ru), cobalt (Co), osmium (Os), chromium (Cr) are preferred, M ₁ is Fe, and M ₂ is Fe or
Most preferred are compounds consisting of the combination Ru.
These compounds can also be used as a second electrochromic layer in a stacked manner or as a mixture. By stacking transition metal mixed valence complexes having different absorption spectra in this manner or by forming a mixture thereof into the second electrochromic layer, light can be absorbed in a wider wavelength range. This results in
The light transmittance can be reduced in the entire wavelength range, and the electrochromic device can have higher contrast.

Further, films of these transition metal mixed valence complexes can be formed by electrodeposition, spin coating, dip coating, or the like.

FIG. 1 shows an electrochromic display element according to an embodiment of the present invention. In FIG. 1, 1 is a first electrochromic layer, 2 is a second electrochromic layer, 3 is a front substrate, 4 is a back substrate, and 5 is a
A transparent electrode made of In ₂ O ₃ , SnO ₂ or the like, 6 a sealing material, and 7 an electrolyte layer. This display element has a first electrochromic layer in a predetermined pattern on an electrode 5 provided on a front substrate 3, and a second electrochromic layer on a counter electrode 5 provided on a back substrate 4. It can be produced in the same manner as a conventional display element except that it is provided on each electrode in advance. That is, the first electrochromic layer and the second electrochromic layer are made to face each other, and the electrodes 5 and 5 are held in parallel with each other via the sealing material 6 to form a cell.
An electrolyte solution may be injected into the cell through an injection port (not shown) provided in advance into the cavity of the cell, and the injection port may be sealed with an epoxy resin or the like to form an electrolyte layer.

As the electrolyte layer, an electrolyte solution in which alkali metal ions such as lithium and sodium are dissolved in a polar organic solvent, or a polymer electrolyte in which a soluble polymer such as polyacrylonitrile is added to these solutions is used.

The invention will be illustrated by the following examples and comparative examples.

Example 1 WO ₃ as the first electrochromic layer
Vacuum deposited to a thickness of 3000 Å and 0.01 of FeCl ₃ and K ₃ Fe(CN) ₆ as the second electrochromic layer.
(mol/l) using Prussian blue (Fe ₄ [Fe(CN) ₆ ] ₃ ) electrodeposited to a thickness of 1000 Å from a mixed aqueous solution, and propylene carbonate in which 1 (mol/l) LiClO ₄ was dissolved as the electrolyte layer. Using this method, a display element having the structure shown in FIG. 1 was manufactured.

Figure 2 shows the transmittance of the above element when it is decolored by curve A.
Curve B shows the transmittance when colored at 10 mc/cm ² . The transmittance of this electrochromic display element was extremely low, averaging just under 10% in the visible region.

Comparative example NiO as the second electrochromic layer
Example 1 except that vacuum deposition was performed using an electron beam to a thickness of 3000 Å, and a 0.1N sulfuric acid aqueous solution was used as the electrolyte.
An electrochromic display device similar to the above was created.

The transmittance of this display element when colored at 10 mc/cm ² is shown by curve C in FIG. The transmittance of this element when colored is higher in the entire visible region than that of the display element of Example 1 described above, and the average transmittance is also approximately 35%.
This was a high value.

Example 2 4 parts by weight of polyaclonitrile as electrolyte layer
An electrochromic display element was prepared in the same manner as in Example 1 except that a polymer ionic conductor in which 2 parts by weight of LiClO ₄ and 3 parts by weight of propylene carbonate were dissolved, and the same results as in Example 1 were obtained. It was done.

Example 3 An electrochromic display element was produced in the same manner as in Example 1 except that MoO ₃ was used as the first electrochromic layer, and the same results as in Example 1 were obtained.

Example 4 Prussian blue used as the second electrochromic layer was coated with FeCl ₃ and Prussian blue on a transparent conductive film.
After forming by spin coating a mixed aqueous solution of K ₃ Fe (CN) ₆ , an electrochromic display element was produced in the same manner as in Example 1. This display element also had an average transmittance of 10% in the visible region, and Example 1
The result was the same.

Example 5 Ruthenium violet ( _{Fe x [ Ru} ( ^CN ) _{6 ]} yHowever, 3≦x
An electrochromic display element was produced in the same manner as in Example 1, except that 1,000 Å of the second electrochromic layer was electrodeposited.
When this display element was driven by applying a voltage of 1.5V, an extremely deep dark blue color was observed when colored. The transmittance of this element during decoloring and coloring is shown by curves D and E in FIG. 3, respectively. The transmittance was significantly lower than that of the comparative example, and the average transmittance in the visible region was about 6%.

Example 6 After electrodepositing Prussian blue to a thickness of 500 Å on a transparent conductive film, the layer was further laminated and ruthenium purple was electrodeposited to a thickness of 700 Å to form a second electrochromic layer. A display element was manufactured. The average transmittance of this element was about 7%.

Example 7 Similarly to Example 6, after electrodepositing Prussian blue at 500 Å and ruthenium purple at 700 Å on the transparent electrode,
Additionally 0.005 (mol/l) FeCl ₃ and K ₃ Co(CN) ₆
Fem[Co(CN) ₆ ]n at 5 (μA/cm ² ) from aqueous solution
Example 1
An electrochromic display element with the following configuration was fabricated. The transmittance of this display element when colored was extremely reduced, with only a slight peak seen around 450 to 470 nm, and the average transmittance in the visible region was less than 5%, and it became almost achromatic.

As is clear from the above results, according to the present invention, the metal oxide layer that develops color in a reduced state is used as the first electrochromic layer, and the transition metal mixed valence complex of formula (1) that develops color in an oxidized state is used as the first electrochromic layer. Since two electrochromic layers are used, both electrochromic layers develop a deep color at the same time when coloring, and both become colorless when decoloring, resulting in an electrochromic display element with high contrast and extremely low transmittance.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of an electrochromic display element according to an example of the present invention, FIG. 2 is a curve diagram showing the transmittance of electrochromic display elements of Example 1 and Comparative Example, and FIG. FIG. 3 is a curve diagram showing the transmittance of an electrochromic display element. 1... first electrochromic layer, 2...
second electrochromic layer, 3... surface substrate,
4... Back substrate, 5... Transparent electrode, 6... Seal material, 7... Electrolyte layer.

Claims (1)

[Claims] 1 A pair of electrodes, at least one of which is translucent, with a first electrochromic layer on the surface of one electrode, and a second electrochromic layer on the surface of the opposing electrode, In an electrochromic display element in which an electrolyte is sealed between two electrodes,
The first electrochromic layer is composed of a metal oxide layer that develops color in a reduced state, and the second electrochromic layer is formed by the following general formula M _1x [M ₂ (CN) ₆ ] y (1) (wherein M ₁ and M ₂ are transition metals, x is 3 to 4,
1. An electrochromic display element comprising a mixed valence complex represented by the formula (y represents 2 to 3).