JPH0114959B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved electrochromic material that reversibly develops and discolors through redox reactions upon application of voltage.

Electrochromic display (below)
(abbreviated as ECD), by applying a voltage between a transparent display electrode and a counter electrode, an oxidation or reduction reaction occurs at the transparent display electrode and a colored pattern is formed. It utilizes a mechanism in which the colored pattern is erased by short-circuiting it with the electrode.

Compared to liquid crystals, which are conventionally used as light-receiving display elements, ECDs that generate and erase colors using this mechanism are easy to see with bright color displays without viewing angle dependence, and have a memory function.
It is attracting attention because it has many excellent features such as a wide operating temperature range and the ability to easily enlarge the screen.

General drawings traditionally used
A configuration diagram of an ECD element is shown. In the figure, 1 is a glass substrate, 2 is a transparent display electrode, 3 is an electrochromic material layer that changes color and fades, 4 is an electrolyte solution, 5 is a spacer, and 6 is a counter electrode.

That is, each transparent display electrode 2 formed on a substrate
A spacer 5 is interposed between the electrode 6 and the counter electrode 6, an electrochromic material layer 3 is provided on the transparent display electrode 2 to constitute an ECD cell, and the space between the spacer 5 and the above electrodes is filled with an electrolyte solution (4). By ECD
Create an element. Generally, in an ECD element, the initially color-developing material is colorless or pale yellow, and the white color of the background plate is visually observed and is white or pale yellow. In addition, between the transparent display electrode 2 as a negative electrode and the counter electrode 6,
When a voltage of 2V is applied, a color display corresponding to the electrochromic material is obtained, and the transparent display electrode 2
The color is erased by applying a voltage opposite to the above voltage between the electrode 6 and the opposing electrode 6, or by short-circuiting the two electrodes.

Typical ECD materials that have been proposed in the past include organic compounds such as low-molecular-weight viologen derivatives (4,4'-bipyridine derivatives) and inorganic compounds such as tungsten oxide (WO ₃ ).

Among these, organic compounds such as low-molecular-weight viologen derivatives have the advantage of providing a more vivid color display than inorganic compounds, and that various colors can be selected by selecting the derivative.

However, ECDs using low-molecular-weight viologen derivative solutions have not reached the level of practical use due to short repeated display life, insufficient memory life, and insufficient response speed. is the current situation.

Using such low-molecular-weight viologen derivatives
As a method to solve the problems in ECD, a method has been proposed in which a transparent display electrode is coated in advance with a polymer obtained from, for example, polyxylyl viologen and polystyrene sulfonic acid, which has a functional group that changes color and disappears when voltage is applied. . However, the types of colors that can be developed are relatively limited, and there is a need for a new material that can develop any color and has good stability in repeated display by color development and fading.

This invention was made to eliminate the drawbacks of the conventional ones, and it was made using polystyrene sulfonic acid and the general formula (In the formula, R is a phenyl group attached with an alkylene group and a sulfone group, and n is a positive integer of 2 to 50.)
By using a polymer complex obtained by reacting a polymerized viologen derivative shown in an aqueous solution with a conductive powder containing a viologen group on the surface, a clear display with various color tones can be obtained. The object of this invention is to obtain an electrochromic material having stable repeatable display characteristics and high-speed response.

The conductive fine powder used in this invention includes tin oxide, indium oxide, zinc oxide, titanium oxide, etc., and those made conductive by heat treatment, mixing with different elements, and surface treatment.

As one method of bonding viologen groups to the surface of these conductive fine powders, bonding with viologen groups using a silane coupling agent is shown in the following reaction formula.

That is, it is known that hydroxyl groups generally exist on the surface of conductive fine powder, and this hydroxyl group is utilized to perform the reaction with the silane coupling agent.
The number of hydroxyl groups can be further increased by acid treatment of the conductive fine powder, and the amount of reaction can be increased.

As the silane coupling agent, chlorosilane, methoxysilane, ethoxysilane, etc. having a halogenated alkyl group can be used. For example, 3-bromopropyltrichlorosilane, 3-chloropropyldimethychlorosilane,
3-chloropropyltrichlorosilane, trichlorosilyl-2-(P,m-chloromethylphenyl)
Ethane, 1-(dimethylchlorosilyl)-2(P,
Examples include, but are not limited to, m-chloromethylphenyl)-ethane, 3-bromopropyltrimethoxysilane, and triethoxysilyl-2-(P,m-chloromethylphenyl)-ethane.

By reacting the conductive fine powder surface-treated with such a silane coupling agent and N-monosubstituted 4,4'-bipyridine, a conductive fine powder to which viologen groups are bonded is obtained. In another way, 4,
By the reaction of 4'-bipyridine and α,w-alkyl dihalide, a structure [] in which viologen groups are polymerized on the surface of conductive fine powder is obtained.

The polymerized viologen derivative used in this invention has the general formula (In the formula, R is a phenyl group attached with an alkylene group and a sulfone group, and n is a positive integer of 2 to 50.)
It is indicated by. If n is outside the above range, it will be difficult to form a polymer complex with the polystyrene sulfonic acid used in this invention.

A polymer ion complex of a polymerized viologen derivative and polystyrene sulfonic acid can be easily obtained as a precipitate by mixing aqueous solutions of the polymerized viologen derivative and polystyrene sulfonic acid sodium salt. As the solvent for the polymer ion complex, a mixed solvent of an organic solvent such as tetrahydrofuran, dioxane, dimethylformamide, acetone, etc., hydrochloric acid, and water is used.

The electrochromic material of the present invention can be obtained, for example, by the method described below. That is, the electroconductive fine powder to which the viologen group is bonded is mixed with a solution of a polymer ion complex of a polymerized viologen derivative and polystyrene sulfonic acid, and the mixture is coated on a transparent display electrode to produce an ECD having a structure similar to that shown in the figure. Create a cell. The material coated on the transparent display electrode in this way becomes insoluble in general organic solvents and water after the solvent is dried and removed, forming a strong film.

As the electrolyte solution to be filled into the cell, a supporting electrolyte is dissolved in water or an organic solvent such as dimethylformamide, acetonitrile, propylene carbonate, or a mixed solvent of water and an organic solvent at a concentration of 0.01 to 5 mol/ml. Examples of supporting electrolytes include lithium chloride, potassium chloride, sodium chloride, potassium bromide, potassium sulfate, ferrous sulfate, potassium perchlorate, lithium perchlorate,
Tetraethylammonium perchlorate, potassium borofluoride, potassium phosphate, potassium acetate, etc. are used.

In the ECD element constructed in this way, the color-generating and decoloring material is initially colorless, and is a white or pale yellow color of conductive fine powder. If a voltage of 1 to 2 V is applied between the transparent display electrode side and the counter electrode, with the side of the transparent display electrode being negative, a display with good contrast can be obtained. The displayed color tone varies depending on the type of polymerized viologen derivative and polystyrene sulfonic acid used and the type of viologen bonded to the surface of the conductive fine powder. In particular, in the case of polymerized viologen derivatives or viologen bonded to the surface of conductive fine powder, the display color can be selected depending on the type of carbon chain bonded to the bipyridium group. For example, when an alkyl group having 3 carbon atoms is used, the color becomes reddish-purple, and as the number of carbon atoms increases to 4 or more, the color becomes blue. It also becomes green when phenyl has an electron-withdrawing group such as a cyano group or a sulfone group.

From this displayed state, the color is quickly erased and returned to the original state by applying a voltage that makes the display electrode positive or by short-circuiting the display electrode and the counter electrode.

This invention will be explained below with reference to examples, but the invention is not limited thereto.

Example 1 50g of conductive tin oxide was treated with acid, thoroughly dried, and 15g of bromopropyltrichlorosilane was added.
was heated and stirred in benzene. Separately, after cleaning, N
-Monopropyl-4,4'-bipyridinium bromide (10 g) was heated and stirred in dimethylformamide at 70°C.

5 g of the conductive powder thus treated and 1 g of a polymer ion complex of polymerized viologen and polystyrene sulfonic acid were dissolved and kneaded in 10 ml of dioxane, 1 ml of water, and 10 ml of concentrated hydrochloric acid, and the mixture was coated on a transparent display electrode. Use this to configure an ECD cell,
Inject 0.3mol/aqueous solution of sodium sulfate
An ECD element was created.

Between the transparent display electrode and the counter electrode as a negative electrode.
When a voltage of 1.0V was applied, a current indicating that a reduction reaction was occurring was observed, and at the same time, a blue-purple display with good contrast was obtained. This reflectance change is 70% when using untreated conductive tin oxide.
It reached 78% compared to the previous year. By applying a voltage in the opposite direction, it quickly returned to its original white color, and this cycle of coloring and decoloring was performed stably.

Example 2 50 g of conductive fine powder having a two-layer structure in which the surface of titanium oxide was coated with tin oxide and 15 g of bromopropyltrichlorosilane were heated and stirred in benzene. solution, after washing, 4,4'-bipyridine 3.12
g, and 4.32 g of tetramethylene bromide were added thereto, and the mixture was heated and stirred in dimethylformamide.

5 g of the conductive powder thus treated and 1 g of a polymer ion complex of polymerized viologen and polystyrene sulfonic acid were dissolved and kneaded in 10 ml of dioxane, 1 ml of water, and 10 ml of concentrated hydrochloric acid, and the mixture was coated on a transparent display electrode. Use this to configure an ECD cell,
Inject 0.3mol/aqueous solution of sodium sulfate
An ECD element was created.

Between the transparent display electrode and the counter electrode as a negative electrode.
When a voltage of 1.0V was applied, a reddish-purple display with good contrast was obtained. This reflectance change reached 75%, compared to 65% when untreated conductive fine powder was used. By applying a voltage in the opposite direction, the original white color was quickly restored, and the repetition of coloring and decoloring was performed stably.

As explained above, this invention utilizes polystyrene sulfonic acid and the general formula (In the formula, R is a phenyl group attached with an alkylene group and a sulfone group, and n is a positive integer of 2 to 50.)
By using a polymer complex obtained by reacting a polymerized viologen derivative shown in an aqueous solution with a conductive powder containing viologen groups on the surface, clear display with various color tones, It has become possible to obtain an electrochromic material with stable repeatable display characteristics and high-speed response.

[Brief explanation of drawings]

The drawing is a configuration diagram of a general ECD element. In the figure, 1 is a glass substrate, 2 is a transparent display electrode, 3 is an electrochromic material layer, 4 is an electrolyte solution, 5 is a spacer, and 6 is a counter electrode.

Claims (1)

[Claims] 1. Polystyrene sulfonic acid and general formula (In the formula, R is a phenyl group attached with an alkylene group and a sulfone group, and n is a positive integer of 2 to 50.)
An electrochromic material comprising a polymer complex obtained by reacting a polymerized viologen derivative shown in an aqueous solution with a conductive powder having a viologen group bonded to its surface.