JPS5828563B2 - Hiyoujitai - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION In recent years, electrochromic displays that reversibly change color through electrode reactions have attracted attention.

However, in this display, it is extremely difficult to uniformly develop and erase color, which has delayed its practical use.

This is partly because when the colored species is deposited on the electrode surface, it is extremely sensitive to the condition of the electrode surface, and conversely, when decoloring, the current flows preferentially from areas where no deposition has occurred. This is because sufficient current does not flow to decolor the deposited colored material.

An object of the present invention is to provide a display body that eliminates these reactions on the non-uniform electrode surface.

Now, as an electrochromic element, N・N'-d
i (n-heptyl) 4-4'-bipri
When something like dibromide is used, it dissociates into ions in an aqueous solution.

When a current is passed through it, the substance is reduced at one electrode,
It becomes a colored species and precipitates on the electrode surface.

This is because this reduced product has hydrophobicity.

However, the adsorption and desorption properties of this reduced substance vary greatly depending on slight differences on the electrode surface.

Therefore, due to the non-uniformity of the electrode, there are areas that are easily colored and areas that are not, and it does not adhere uniformly to the electrode.

Therefore, when used as a display, uniformity cannot be obtained.

This non-uniformity is particularly noticeable when a Nesa electrode is used.

However, when a solvent such as methyl alcohol is used, the reduced product does not precipitate on the electrode surface, but instead floats in a colored state near the electrode.

Now, if we dissolve the above electrochromic element in an aqueous solution and add a substance such as methanol that has a hydrophilic OH group and a hydrophobic hydrocarbon chain to it, the methanol will dissolve uniformly in the water and will also be applied to the surface of the NESA electrode. Gets wet evenly.

If a reduced product is produced in this state, it will not be deposited directly on the electrode surface, but will be deposited on the electrode surface via a layer wetted with alcohol.

Of course, if a large amount of alcohol is present, it will not work well because it will float near the electrode surface, but if a small amount of alcohol is added, the colored material will be uniformly deposited on the electrode surface.

This is thought to be because alcohol molecules lightly and uniformly cover the entire electrode surface, thereby eliminating non-uniformity of the electrode itself.

Therefore, the hydrophobic reductant is uniformly deposited on the electrode surface via the uniformly deposited alcohol.

Therefore, even when erasing is performed using a reverse electric field, the current flows only in areas where there is no colored body and the resistance is low, so that no unerasable portions occur, and the entire surface is erased uniformly.

This is also due to the fact that the original electrochromic substance is more soluble in water than in alcohol.

In other words, when a reverse electric field is applied to the reductant and it becomes the original electrochromic element, it is more likely to splinter in the water than in the alcohol on the electrode surface.

Therefore, the reduced substance on the electrode surface returns to its original state and quickly dissolves into the aqueous solution.

However, in an aqueous solvent containing alcohol, the speed of color development and decolorization becomes extremely slow.

This is considered to be because the diffusion speed of electrons or ions through the alcohol layer is extremely slow.

The only way to increase the reaction speed is to increase the applied voltage.

However, when the applied voltage is increased, a side reaction 2Br occurs on the counter electrode side.
-→Br2↑+2e occurs and reversibility is lost.

If ferrocyanine ions are further added to the alcohol-added aqueous solution, this side reaction can be suppressed.

This is 2F instead of the reaction of 2Br-→Br2↑+2e.
e(CN)#! 2Fe(CN), Ni-2e reaction occurs, thus suppressing the generation of Br2.

Further, Fe(CN)a- and Fe3+ ions involved in this reaction are both water-soluble and cause a reversible reverse reaction.

Therefore, the irreversible reaction of Br2 gas generation can be prevented by an alternative reversible reaction.

In other words, the addition of alcohol prevents uneven precipitation on the electrode surface, which increases the operating voltage to prevent the reaction speed from slowing down, and the addition of ferrocyanine ions prevents side reactions that occur due to the increased operating voltage. Ta.

Examples 2.3 will be shown below.

Example 1 0.3 mo1/e of auxiliary electrolyte KBr was added to a 0.1 mo1/1 aqueous solution, and methanol was adjusted to 5% with respect to water.
Added.

Add a small amount of ferrocyanic potash (to an extent that does not cause dark coloring, as too much will cause coloring of the liquid and reduce the display effect).

This solution is sealed in a cell as shown in Figure 1, and the gap between the electrodes is 1.
3, apply a voltage of 1.4 to 1.5 .mu.

A colored substance appears on the cathode side and can be erased by reversing the voltage.

By this method, it was possible to perform a uniform coloring/decoloring reaction at a voltage that does not cause water electrolysis.

Sufficient time to write and erase is 5V at 1.4V.
Q Om 36c/1 cycle was possible.

Moreover, when the voltage is set to 1.6V, 300 m se
A response speed of c was obtained, and there were no practical problems (on wristwatches, calculators, and other various display devices).

Furthermore, the lifespan did not change even after 106 cycles or more of coloring and decoloring.

In Example 1, methanol was replaced with ethanol.

The results were as follows: 1 drive voltage was required to be about 1.6 square meters, but other aspects were almost the same as in Example 1, and the results were good.

Example 2 In Example 1, a small amount of ferric chloride was used instead of ferrocyanide ions, but the same effect as in Example 1 was obtained.

In this case, when driving was performed 3×10 6 times or more, colored precipitates appeared near the electrodes.

However, when we used a three-terminal constant potential drive method instead of three-terminal drive, we were able to set the potential so that it did not appear near the segment electrodes, but only on the opposite anode electrode. Since it is possible to hide it with a partition plate or the like, there is no problem in practical use.

See Figure 2 for the drive circuit. Example 3 In Example 1, sodium alkylbenzenesulfonate was added instead of methanol.

This also has a hydrocarbon chain and a hydrophilic group, has a strong effect of eliminating non-uniformity on the surface of the NESA electrode, is stable even in solution, and was able to obtain good results.

In addition, it was found that surfactants that do not react with electrochromic, ferrocyanian ions, or iron ions have the effect of uniformizing coloring and fading on the electrodes, and can be used in displays.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the display cell used in the example, and a
is a sectional view, and b is a plan view. 11: Substrate ceramics, 12 Varnish spacer-11314
: Nesa electrode, 15: Cover glass. FIG. 2 is a schematic diagram of a three-terminal constant potential drive circuit used in Example 2. 21: Operational amplifier, 22: Display cell (for three electrodes), 23
: counter electrode (hidden electrode), 24: reference electrode (potential reference electrode), 25: working electrode (segment electrode), 26: drive signal voltage.

Claims (1)

[Claims] 1. In a display using a viologen bromide electrochromic element that reversibly changes color through an electrode reaction in a solution, either ferric chloride or ferrocyanide ion and methanol, ethanol or benzenesulfon are added to the solution. Add any one type of sodium acid,
A display body characterized in that a Nesa electrode or an indium oxide transparent electrode is used as an electrode.