JPS6334914B2 - - Google Patents

Description

[Detailed Description of the Invention] This invention provides the following methods:
This invention relates to an electrochromic display material that reversibly develops and discolors.

Electrochromic display (below)
(abbreviated as ECD), by applying a DC voltage, an oxidation or reduction reaction occurs at the transparent display electrode to form a colored pattern, and by applying a reverse voltage, this colored pattern is caused by a reverse reaction. It uses a mechanism that erases color.

ECD generates and erases color using this mechanism.
consumes about the same amount of power as liquid crystals, which have traditionally been used as light-receiving display elements.
Moreover, it has many excellent features such as no dependence on the current viewing angle, bright color display for easy viewing, memory function, wide operating temperature range, and ease of making the screen larger. It is attracting attention because of this.

Typical ECD materials that have been proposed include organic compounds such as viologen derivatives (4,4'-bipyridine derivatives) and inorganic compounds such as tungsten oxide (WO ₃ ) and molybdenum oxide (MOO ₃ ). .

Among these, viologen derivatives have the advantage of providing a more vivid color display than inorganic compounds, and can also produce a variety of colors depending on the selection of the derivative. The ECD used has not reached the level of practical use due to its short repeated display life or insufficient memory life.

Here, it is believed that the color development and decolorization reactions of the viologen derivative at the electrode follow the following formula.

That is, the viologen derivative ( ) is reduced by the application of a negative voltage to become a colored radical cation ( ), and forms a salt with the counter ion X ^- to become insoluble in water and precipitate on the electrode surface.
When the voltage application is stopped in this state, the colored state is maintained as it is and exhibits a memory effect. To decolor, applying a voltage in the opposite direction oxidizes and returns to the state of () again, becoming a colorless, uniform solution state. Furthermore, at this time, in the redox reaction at the electrode, if side reactions other than the above reaction formula occur, or if the state () is further reduced and progresses to the second reduced state, it will adversely affect the repeatable display life. It's what it does.

Also, a major feature of ECD is that it has memory characteristics, and can retain the display in the written state without consuming power. This makes it difficult to repeat stable color development and decolorization. The reason for this difficulty in decoloring is that the radical cation salt in the above state () gradually crystallizes on the electrode surface, reducing the rate of oxidation reaction when a reverse voltage is applied. Although it is thought that this phenomenon is caused by display coloration-
This is extremely undesirable for ECDs, as it causes colored matter to gradually accumulate when decoloring is repeated, and when displaying using a memory function, complete decolorization becomes impossible as the memory time increases. The result is no result.

Therefore, there is a need for a new ECD display material that does not crystallize in a coloring state and can repeat stable coloring and decoloring reactions.

This invention is an ECD to satisfy the above requirements.
The ECD display material according to the present invention is a viologen compound derivative having an organic substituted phosphate ester anion or an organic substituted phosphonate anion as a counterion, which is represented by the following general formula. be.

(However, in the formula, R ₁ and R ₂ represent an alkyl group, an allyl group, an aralkyl group, and X ^- ₁ is (R ₃ -O) ₂ P (=
O) Phosphate anion denoted by ^O- , R ₄
- Phosphonate anion represented by P(=O)ONaO ^- or (R ₅ ) ₂ P(=O)O ^- , and X ^2- ₂ is R ₆
They are _a phosphate anion represented by -OP(=O) ^O2-2 and _a phosphonate anion represented by _R7 -P(=O) ^O2-2 . Further, R ₃ to R ₇ represent an alkyl group, an allyl group, or an aralkyl group. ) Here, examples of viologen compound derivatives include:
N,N'-dimethyl viologen, N,N'-diethyl viologen, N,N'-diheptyl viologen,
Examples of counterions include N,N'-didodecyl viologen, N,N'-diphenyl viologen, N,N'-di-P-cyanophenyl viologen, and N,N'-dibenzyl viologen. is 1
dimethyl phosphate, as the valent anion;
Phosphate ester anions such as diethyl phosphate, didecyl phosphate, diphenyl phosphate, dibenzyl phosphate, dimethyl phosphonate, diethyl phosphonate,
Phosphonic acid anions such as didecyl phosphonate, diphenyl phosphonate, dibenzyl phosphonate, etc.; as divalent anions, methyl phosphonate, ethyl phosphonate, decyl phosphonate, phenyl phosphonate; , phosphate ester anions such as benzyl phosphonate, phosphonate anions such as methyl phosphonate, ethyl phosphonate, decyl phosphonate, phenyl phosphonate, benzyl phosphonate, and polyethylene glycol phosphate. Examples include esters.

In order to construct an ECD element using these ECD display materials, the ECD display material must be mixed with water, an organic solvent such as DMF, or a mixed solvent of water and an organic solvent at 1×10 ^-5 ~0.5 mol/
It is dissolved or dispersed at a concentration of , and a supporting electrolyte is mixed in for the purpose of increasing conductivity and lowering power consumption. Examples of this supporting electrolyte include lithium chloride, potassium chloride, sodium chloride, potassium bromide, potassium sulfate, ferrous sulfate, potassium perchlorate, lithium perchlorate, potassium borofluoride, potassium phosphate, potassium acetate, etc. depending on the purpose
It is used in a range of 0.01 to 1 mol/. Furthermore, in order to facilitate adsorption and desorption of colored substances due to redox reactions on the electrode surface, ethylene glycol, surfactants, etc. are added, and nitrogen is added to suppress side reactions caused by dissolved oxygen. It is also effective to deoxidize the material by passing a gas through the material.

However, the ECD display material prepared in this way is
It is sealed in the ECD cell shown in FIG. That is,
In this FIG. 1, 1 and 1 are the substrate, 2 and 3
are transparent display electrodes and counter electrodes inside the substrate; 4;
4 is a spacer between the substrates, and 5 is an ECD solution.

In the configuration shown in FIG. 1, when a voltage with the display electrode 2 side being negative is applied between the transparent display electrode 2 and the counter electrode 3, a bright display is developed on the display electrode 2, and this display Even if the voltage is cut off, it remains as it is and exerts a memory effect, and when voltage is applied in the opposite direction, the display disappears and returns to its original state, and this operation can be repeated. did it.

In addition, the voltage to start coloring, the voltage to start decoloring, and the time to continue the memory action,
The color tone of the developed color depends entirely on the properties of the viologen compound derivative, and in particular, the ease with which the color is erased after retaining the memory effect is different from that of the organic substituted phosphate ester anion or organic substituted phosphonate anion in this invention. When used as an ion, it is significantly improved compared to when a conventional halogen ion or the like is used as a counter ion.

This is because by using an organic substituted phosphate ester anion or an organic substituted phosphonate anion as a counterion, the colored substance ( ) that is reduced and precipitated at the electrode according to the above reaction formula becomes difficult to crystallize, and is easily reversed. This is thought to be because the oxidation reaction due to voltage progresses and the color becomes easier to fade. Based on such difficulty in crystallization, it is possible to prevent colored substances from accumulating on the electrode surface during repeated display, and even when display colors are developed due to the memory effect, color erasure proceeds smoothly. This will have a great effect on extending the life of the ECD element.

As detailed above, when the ECD display material according to the present invention is used, it is easy to erase the color after the memory action, improving the memory display, extending the service life with repeated display, and achieving high reliability.
It is possible to obtain an ECD element.

Next, each embodiment of the present invention will be specifically described.
Note that, of course, the present invention is not limited to these embodiments.

Example A 0.1 mol/l of K ₂ SO ₄ was added as a supporting electrolyte to an aqueous solution of 0.05 mol/l of N,N'-diheptylviologen di-diphenyl phosphate, and the ECD cell shown in FIG. 1 was prepared. It was enclosed in.

When a voltage was gradually applied to this with the transparent display electrode side set as negative, a current was observed indicating that the ECD solution was undergoing a reduction reaction, and at the same time a purple display with good contrast was obtained on the transparent display electrode. When voltage application was stopped in this colored state, the display was maintained for several tens of hours, and the color quickly disappeared when voltage was applied in the opposite direction.

The applied voltage pulse width for color development is 0.5 seconds, the memory time is 1 minute, and the applied voltage pulse width for decolorization is 0.5 seconds.
When this coloring-memory-erasing operation was repeated for 0.5 seconds, with N,N'-diheptylviologen and dibromide, colored matter was observed to accumulate on the display electrode within several days, and the display quality deteriorated. However, with the composition of Example A, no deposits due to unfading were observed even after one month, and stable display quality was exhibited.

Example B N,N'-dibenzylviologen phenyl phosphonate was sealed in an ECD cell in the same manner as in Example A except that N,N'-dibenzylviologen phenyl phosphonate was used, and by applying a voltage with the transparent display electrode side as negative, a red A purple display with good contrast was obtained.

When repeated operations of coloring and decoloring were performed under the same conditions as in Example A, the repeated display characteristics were stable, and no deposits due to unfading were observed even after one month had elapsed.

Example C N,N'-di-P-cyanophenyl viologen di-didecyl phosphate was sealed in an ECD cell in the same manner as in Example A, with the transparent display electrode side being negative, and the voltage By applying , a green display with good contrast was obtained.

When repeated operations of coloring and decoloring were performed under the same conditions as in Example A, the repeated display characteristics were stable, and no deposits due to unfading were observed even after one month had elapsed.

[Brief explanation of the drawing]

The drawing is a cross-sectional view showing the general configuration of an ECD cell. DESCRIPTION OF SYMBOLS 1... Substrate, 2... Transparent display electrode, 3... Counter electrode, 4... Spacer, 5... ECD solution.

Claims (1)

[Scope of Claims] 1. In an electrochromic display that utilizes the redox-induced decolorization reaction of the following viologen compound derivative, the counter ion of the derivative is an organic substituted phosphate ester anion or an organic substituted phosphonate anion. An electrochromic display material characterized by the following. (However, in the formula, R ₁ and R ₂ represent an alkyl group, an allyl group, or an aralkyl group. Also, X ^- ₁ is (R ₃ -O)
Phosphate ester anion represented by ₂ P(=0)O ^- , R ₄ -P(=0)ONaO ^- or (R ₅ ) ₂ P(=0)
It is a phosphonate anion denoted by O ^- , and X ^2- ₂
is _a phosphate anion represented by R ₆ -OP(= ₀ )O ^2-2 and a phosphonate anion represented by R ₇ -P(=0)O ^2-2 . Here, R ₃ to R ₇ represent an alkyl group, an allyl group, or an aralkyl group. )