JP5617597B2 - Electrochromic compound, electrochromic composition, and display element - Google Patents

Description

  The present invention relates to an electrochromic compound, an electrochromic composition, and an electrochromic compound or an electrochromic composition that exhibit cyan coloration during color development.

In recent years, electronic paper has been actively developed as an electronic medium replacing paper.
Since electronic paper is characterized in that the display device is used like paper, characteristics different from those of a conventional display device such as a CRT or a liquid crystal display are required. For example, it is a reflection type display device, has a high white reflectance and a high contrast ratio, can display a high definition, has a memory effect in display, can be driven even at a low voltage, is thin and light, and is inexpensive It is necessary to have characteristics such as Of these, the white reflectance / contrast ratio equivalent to that of paper and the demand for color display are particularly high as characteristics relating to display quality.

  Until now, as a display device for electronic paper, for example, a method using a reflective liquid crystal, a method using electrophoresis, a method using toner migration, and the like have been proposed. However, it is very difficult for any of the above methods to perform multicolor display while ensuring white reflectance / contrast ratio. In general, in order to perform multicolor display, a color filter is provided. However, if a color filter is provided, the color filter itself absorbs light, and the reflectance decreases. Furthermore, since the color filter divides one pixel into red (R), green (G), and blue (B), the reflectance of the display device is lowered, and the contrast ratio is lowered accordingly. When the white reflectance / contrast ratio is significantly reduced, the visibility is very poor and it is difficult to use as electronic paper.

Patent Documents 1 and 2 propose a reflective color display medium in which a color filter is formed on an electrophoretic element. However, since the reflective color display media described in Patent Documents 1 and 2 have a low white reflectance and a low contrast ratio, good image quality cannot be obtained even if a color filter is formed on such a display medium. Is obvious.
Patent Documents 3 and 4 propose an electrophoretic element that performs colorization by moving particles colored in a plurality of colors. However, even if these methods are used, in order to perform multicolor display, it is necessary in principle to divide one pixel into three, so that the division problem is not solved, and a high white reflectance and a high contrast ratio are achieved. It cannot be satisfied at the same time.

On the other hand, as a promising technique for realizing a reflective display device without providing the color filter as described above, there is a method using an electrochromic phenomenon.
Electrochromism is a phenomenon in which when a voltage is applied, an oxidation / reduction reaction occurs reversibly in accordance with the polarity, and the color changes reversibly following. An electrochromic display device is a display device that utilizes the coloring or decoloring (substantially, color erasing) of an electrochromic compound that causes this electrochromic phenomenon. Since this electrochromic display device is a reflective display device, has a memory effect, and can be driven at a low voltage, it is a leading candidate for display device technology for electronic paper use, from material development to device design. R & D has been conducted extensively.

  However, the electrochromic display device has a drawback in that the response speed of color development / decoloration is slow because of the principle of performing color development / decoloration utilizing oxidation / reduction reactions. For example, Patent Document 5 describes an example in which an electrochromic compound is fixed in the vicinity of an electrode to improve the response speed of color development and decoloration. According to the description of Patent Document 5, the time required for color development and decoloration, which has been about several tens of seconds, has been improved to about 1 second for both the color development time from colorless to blue and the color elimination time from blue to colorless. Yes. However, this is not sufficient, and in the research and development of electrochromic display devices, it is necessary to further improve the response speed of color development and decoloration.

  An electrochromic display device is expected as a multicolor display device because various colors can be developed depending on the structure of an electrochromic compound used as a display material. In particular, since an electrochromic compound reversibly changes between a colorless state and a color coloring state, a multicolor display can be realized by stacking the electrochromic compounds capable of coloring different colors. . In color display with a laminated structure using an electrochromic compound, it is not necessary to divide one pixel into red (R), green (G), and blue (B) as in the prior art. There is also an advantage that the contrast ratio does not decrease.

There are some published examples of multicolor display devices using the electrochromic display method. For example, Patent Document 6 proposes a multicolor display device using an electrochromic compound in which fine particles of a plurality of types of electrochromic compounds are stacked, and has a high functionality having a plurality of functional functional groups with different applied voltages that exhibit color development. An example of a multicolor display device in which a plurality of electrochromic compounds made of molecular compounds are stacked to form a multicolor display electrochromic compound is described.
Further, Patent Document 7 proposes a display device in which electrochromic layers are formed in multiple layers on an electrode, and a multicolor color is developed using a difference in voltage value or current value necessary for the color development. An example of a multi-color display device having a display layer formed by laminating or mixing a plurality of electrochromic compounds having different color threshold voltages and different charge amounts necessary for color development is described.
Patent Document 8 proposes an electrochromic device having a porous electrode in which a pyridine compound is adsorbed on one of the pair of electrode structures, and the electrochromic layer is interposed between the pair of transparent electrodes. An example of a multicolor display device in which a plurality of structural units sandwiching (pyridine compound) and an electrolyte is laminated is described.

  However, the viologen-based organic electrochromic compounds exemplified in Patent Documents 5, 6, and 7 are those that develop blue and green colors, and those that produce the three primary colors yellow, magenta, and cyan necessary for full colorization. is not. In order to develop the three primary colors, sharp light absorption at the time of color development is required. In particular, cyan color development must have sharp absorption in the long wavelength region, cyan color development is possible, and color development or disappearance is stable. Until now, no electrochromic compound capable of color (decoloration) has been obtained. Also in Patent Document 8, an electrochromic compound that develops cyan is studied, but the color purity is not satisfied.

  The present invention has been made in view of the above-described problems in the prior art, and shows an electrochromic compound that exhibits sharp light absorption spectrum characteristics during color development and exhibits color development in a cyan system, and the electrochromic compound is conductive or semiconducting nano It is an object of the present invention to provide an electrochromic composition bonded or adsorbed to a structure, and a display element using an electrochromic compound or an electrochromic composition.

As a result of intensive studies, the present inventors have found that the above problems can be solved by the inventions described in the following [1] to [ 4 ], and have reached the present invention. Hereinafter, the present invention will be specifically described.

[1]: The above problem is solved by an electrochromic compound represented by the following general formula (A) .

[Wherein, R ₁ and R ₂ each independently represents an alkyl group. ]

[ 2 ]: The above problem is solved by an electrochromic composition characterized in that the electrochromic compound according to [1] is bonded or adsorbed to a conductive or semiconducting nanostructure.

[ 3 ]: The above-described problem includes a display electrode, a counter electrode disposed opposite to the display electrode at an interval, and an electrolyte disposed between the two electrodes, the counter electrode side of the display electrode This is solved by a display element comprising a display layer containing the electrochromic compound according to [1] on the surface of the display.

[ 4 ]: In the display element described in [ 3 ] above, the display layer is the electrochromic composition described in [ 2 ].

  According to the present invention, it is possible to obtain an electrochromic compound or an electrochromic composition that exhibits sharp light absorption spectral characteristics during color development and exhibits cyan color development. Further, by using the electrochromic compound or the electrochromic composition of the present invention, a display element capable of full color display can be provided in combination with an electrochromic compound that develops yellow and magenta.

It is the schematic which shows the structural example of the general display element using the electrochromic compound of this invention. It is the schematic which shows the structural example of the general display element using the electrochromic composition of this invention. It is a figure which shows the light absorption spectrum at the time of color development of the electrochromic display element produced in Example 4. FIG. It is a figure which shows the light absorption spectrum at the time of color development of the electrochromic display element produced in the comparative examples 1 and 2. FIG.

  As a result of intensive studies to solve the above problems, the present inventors have found that the above problems can be solved if the electrochromic compound has a structure represented by the following general formula (I). That is, the electrochromic compound represented by the general formula (I) exhibits sharp light absorption spectrum characteristics during color development and exhibits cyan color development.

[Wherein, R ₁ and R ₂ each independently represents an alkyl group, and X ₁ , X ₂ , X ₃ , X ₄ , X ₅ , X ₆ , X ₇ , X ₈ are each independently a hydrogen atom or a halogen atom] Hydroxyl group, nitro group, cyano group, carboxyl group, carbonyl group, amide group, aminocarbonyl group, sulfonic acid group, sulfonyl group, sulfonamide group, aminosulfonyl group, amino group, alkyl group, alkenyl group, alkynyl group, A monovalent group selected from an aryl group, an alkoxy group, an aryloxy group, an alkylthio group, an arylthio group, and a heterocyclic group is shown, and these monovalent groups may have a substituent. L ₁ and L ₂ each independently represent a monovalent group selected from an alkyl group, an alkenyl group, an alkynyl group, and an aryl group, and these monovalent groups may have a substituent. A ⁻ and B ⁻ each represents a monovalent anion. ]

  Here, the carbonyl group includes an alkoxycarbonyl group, an aryloxycarbonyl group, an alkylcarbonyl group, an arylcarbonyl group, and the like, and the aminocarbonyl group includes a monoalkylaminocarbonyl group, a dialkylaminocarbonyl group, and a monoarylaminocarbonyl group. Group, diarylaminocarbonyl group and the like, as the sulfonyl group, alkoxysulfonyl group, aryloxysulfonyl group, alkylsulfonyl group, arylsulfonyl group and the like, and as the aminosulfonyl group, monoalkylaminosulfonyl group, dialkylaminosulfonyl Group, monoarylaminosulfonyl group, diarylaminosulfonyl group and the like, examples of the amino group include monoalkylamino group, dialkylamino group and the like, These monovalent groups may have a substituent.

That is, as specific examples of X ₁ , X ₂ , X ₃ , X ₄ , X ₅ , X ₆ , X ₇ , X ₈ , hydrogen atom, halogen atom, hydroxyl group, nitro group, cyano group, carboxyl group, substituent An alkoxycarbonyl group which may have a substituent, an aryloxycarbonyl group which may have a substituent, an alkylcarbonyl group which may have a substituent, an arylcarbonyl group which may have a substituent An amide group, an optionally substituted monoalkylaminocarbonyl group, an optionally substituted dialkylaminocarbonyl group, an optionally substituted monoarylaminocarbonyl group, a substituent May have a diarylaminocarbonyl group, a sulfonic acid group, an optionally substituted alkoxysulfonyl group, and may have a substituent A reeloxysulfonyl group, an alkylsulfonyl group which may have a substituent, an arylsulfonyl group which may have a substituent, a sulfonamide group, a monoalkylaminosulfonyl group which may have a substituent, A dialkylaminosulfonyl group which may have a substituent, a monoarylaminosulfonyl group which may have a substituent, a diarylaminosulfonyl group which may have a substituent, an amino group and a substituent. A monoalkylamino group which may have a substituent, a dialkylamino group which may have a substituent, an alkyl group which may have a substituent, an alkenyl group which may have a substituent, and a substituent. An alkynyl group which may have, an aryl group which may have a substituent, an alkoxy group which may have a substituent, and a substituent. An aryloxy group which may have a substituent alkylthio group which may have a substituent arylthio group, and a heterocyclic group which may have a substituent.
Substituents of X ₁ , X ₂ , X ₃ , X ₄ , X ₅ , X ₆ , X ₇ and X ₈ can impart solubility to the solvent of the electrochromic compound, thereby facilitating the device manufacturing process. . In addition, the color development spectrum (color) can be adjusted. On the other hand, the stability such as heat resistance and light resistance is likely to be lowered by these groups. Therefore, a hydrogen atom, a halogen atom, or a substituent having 6 or less carbon atoms is preferable.

Specific examples of L ₁ and L ₂ include an alkyl group which may have a substituent, an alkenyl group which may have a substituent, an alkynyl group which may have a substituent, and a substituent. And an aryl group which may have
At least one of L ₁ and L ₂ is preferably a functional group that can be directly or indirectly bonded to a hydroxyl group. Such a functional group that can be directly or indirectly bonded to a hydroxyl group may be any functional group that can be directly or indirectly bonded to a hydroxyl group by hydrogen bonding, adsorption, or chemical reaction. Although the structure is not limited, preferred examples include phosphonic acid groups, phosphoric acid groups, carboxyl groups, trichlorosilyl groups, trialkoxysilyl groups, monochlorosilyl groups, monoalkoxysilyl groups, and the like.
The trialkoxysilyl group is preferably a triethoxysilyl group or a trimethoxysilyl group. Of these, trialkoxysilyl groups and phosphonic acid groups, which have a high binding force to conductive or semiconducting nanostructures, are particularly preferred.

In addition, A ⁻ and B ⁻ each represent a monovalent anion and are not particularly limited as long as they are stably paired with a cation moiety, but Br ion (Br ⁻ ), Cl ion (Cl ⁻ ), ClO ₄ ion (ClO ₄ ⁻ ), PF ₆ ion (PF ₆ ⁻ ), BF ₄ ion (BF ₄ ⁻ ), and CF ₃ SO ₃ ion (CF ₃ SO ₃ ⁻ ). Is preferred.

The electrochromic compound of the present invention has an X (X ₁ , X ₂ , X ₃ , X ₄ , X ₅ , X ₆ , X ₇ , X ₈ ) in which the structure of the general formula (I) is symmetrical. ) And L (L ₁ , L ₂ ) are desirable from the viewpoint of ease of synthesis and improvement of stability.
Moreover, although the electrochromic compound of the present invention exhibits cyan coloration, yellow or magenta coloration is also possible due to the effect of the substituent.

  Specific examples of the electrochromic compound of the present invention are shown in the following structural formulas (1) to (10), but the electrochromic compound of the present invention is not limited thereto.

Moreover, the electrochromic composition according to the present invention is obtained by bonding or adsorbing the electrochromic compound of the present invention [electrochromic compound represented by the general formula (I)] to a conductive or semiconducting nanostructure. It is characterized by.
When used in an electrochromic display element, the electrochromic composition of the present invention exhibits cyan color development and further has excellent image memory properties, that is, color image retention characteristics. Note that the conductive or semiconducting nanostructure is a structure having nanoscale unevenness such as a nanoparticle or a nanoporous structure.

When the electrochromic compound of the present invention has a sulfonic acid group, a phosphoric acid group, or a carboxyl group as a bond or adsorption structure, the electrochromic compound is easily complexed with the nanostructure and has excellent electrochromic image retention. It becomes a chromic composition. A plurality of the sulfonic acid group, phosphoric acid group and carboxyl group may be present in the compound.
In addition, when the electrochromic compound of the present invention is bonded to the nanostructure through a silanol bond, the bond becomes strong, and a stable electrochromic composition is obtained. The silanol bond here is a chemical bond through a silicon atom and an oxygen atom. Moreover, the electrochromic composition should just have the structure which the said electrochromic compound and the said nanostructure couple | bonded through the silanol bond, and the coupling | bonding method and form in particular are not limited.

  The material constituting the conductive or semiconducting nanostructure is preferably a metal oxide in terms of transparency and conductivity. Examples of such metal oxides include titanium oxide, zinc oxide, tin oxide, aluminum oxide (approximately, alumina), zirconium oxide, cerium oxide, silicon oxide (approximately, silica), yttrium oxide, boron oxide, magnesium oxide. , Strontium titanate, potassium titanate, barium titanate, calcium titanate, calcium oxide, ferrite, hafnium oxide, tungsten oxide, iron oxide, copper oxide, nickel oxide, cobalt oxide, barium oxide, strontium oxide, vanadium oxide, aluminosilicate A metal oxide mainly composed of acid, calcium phosphate, aluminosilicate or the like is used. Moreover, these metal oxides may be used independently and 2 or more types may be mixed and used.

  In view of electrical properties such as electrical conductivity and physical properties such as optical properties, it is selected from titanium oxide, zinc oxide, tin oxide, alumina, zirconium oxide, iron oxide, magnesium oxide, indium oxide, and tungsten oxide. When one kind or a mixture thereof is used, multicolor display excellent in response speed of color development and decoloration is possible. In particular, when titanium oxide is used, it is possible to display a multicolored color with an excellent response speed of color development and decoloration.

The shape of the metal oxide is preferably metal oxide fine particles having an average primary particle diameter of 30 nm or less. As the particle diameter is smaller, the light transmittance with respect to the metal oxide is improved, and a shape having a larger surface area per unit volume (hereinafter referred to as “specific surface area”) is used. By having a large specific surface area, the electrochromic compound is more efficiently supported, and a multicolor display with an excellent display contrast ratio for color development and decoloration is possible. Although the specific surface area of a nanostructure is not specifically limited, For example, it can be 100 m < ² > / g or more.

Next, the display element according to the present invention will be described.
The display element of the present invention includes a display electrode, a counter electrode disposed opposite to the display electrode at an interval, and an electrolyte disposed between the two electrodes. It has the display layer containing the electrochromic compound represented by the said general formula (I) on the surface.
FIG. 1 shows a configuration example of a general display element using the electrochromic compound of the present invention.
As shown in FIGS. 1A and 1B, the display elements 10 and 20 of the present invention include a display electrode 1, a counter electrode 2 provided to face the display electrode 1 with a space therebetween, An electrolyte 3 disposed between both electrodes (the display electrode 1 and the counter electrode 2), and at least the electrochromic compound (organic electrochromic compound) according to the present invention on the surface of the display electrode 1 on the counter electrode 2 side. It has the display layer 4 containing 4a.
In the display element of FIG. 1B, the display layer 4 is formed on the surface of the display electrode 1 on the counter electrode 2 side using the electrochromic compound of the present invention. As the formation method, any method such as dipping, dipping method, vapor deposition method, spin coating method, printing method, and ink jet method may be used.
Moreover, it is also possible to make it the solution structure which melt | dissolved electrolyte in the solvent like Fig.1 (a), and also to dissolve an electrochromic compound in the said solution. In this case, the electrochromic compound is colored by the redox reaction only on the surface of the display electrode 1.
As shown in the schematic diagram of FIG. 1 (c), the electrochromic compound 4a of the present invention has a functional group (adsorptive group) 4a ₁ that can be directly or indirectly bonded to a hydroxyl group in the molecular structure. If it is present, the adsorptive group is adsorbed on the display electrode 1 to form the display layer 4. Reference numeral 4a ₃ redox coloring portion in FIG. 1 (c), 4a ₂ represents a spacer unit (molecular main skeleton).

Moreover, the display layer containing the electrochromic compound represented by the said general formula (I) can be made into the said electrochromic composition. In FIG. 2, the structural example of the general display element using the electrochromic composition of this invention is shown.
As shown in FIG. 2, the display element 30 of the present invention includes a display electrode 1, a counter electrode 2 provided to face the display electrode 1 at an interval, and both electrodes (the display electrode 1 and the counter electrode). 2) an electrolyte 3 disposed between them, and a display layer 5 containing at least the electrochromic composition 5a of the present invention on the surface of the display electrode 1 on the counter electrode 2 side. The counter electrode 2 has a white reflective layer 6 made of white particles on the display electrode 1 side.

In the display element of FIG. 2, the display layer 5 is formed on the surface of the display electrode 1 on the counter electrode 2 side using the electrochromic composition of the present invention. As the formation method, any method such as dipping, dipping method, vapor deposition method, spin coating method, printing method, ink jet method or the like may be used.
As shown in FIG. 1 (c), the electrochromic compound in the electrochromic composition of the present invention has a functional group (adsorbing group) that can be directly or indirectly bonded to a hydroxyl group in the molecular structure, so-called bond. Since what has group can be used, the said coupling group can couple | bond with electroconductive or semiconducting nanostructure, and can comprise an electrochromic composition. Then, the electrochromic composition is provided in layers on the display electrode 1 to form the display layer 5.

Hereinafter, constituent materials used for the electrochromic display elements 10, 20, and 30 according to the embodiment of the present invention will be described.
As a material constituting the display electrode 1, it is desirable to use a transparent conductive substrate. The transparent conductive substrate is preferably glass or a plastic film coated with a transparent conductive thin film. The transparent conductive thin film material is not particularly limited as long as it is a conductive material, but a transparent conductive material that is transparent and excellent in conductivity is used because it is necessary to ensure light transmission. . Thereby, the visibility of the color to develop can be improved more.
As the transparent conductive material, it is possible to use an inorganic material such as tin-doped indium oxide (abbreviation: ITO), fluorine-doped tin oxide (abbreviation: FTO), or antimony-doped tin oxide (abbreviation: ATO). In particular, it is an inorganic material containing any one of indium oxide (hereinafter referred to as In oxide), tin oxide (hereinafter referred to as Sn oxide), or zinc oxide (hereinafter referred to as Zn oxide). Preferably there is. In oxides, Sn oxides, and Zn oxides are materials that can be easily formed by a sputtering method, and are excellent in transparency and electrical conductivity. Particularly preferable materials are InSnO, GaZnO, SnO, In ₂ O ₃ and ZnO.
Examples of the material constituting the display substrate (not shown) on which the display electrode 1 is provided include glass or plastic. If a plastic film is used as the display substrate, a lightweight and flexible display element can be manufactured.

As the counter electrode 2, a transparent conductive film such as ITO, FTO, or zinc oxide, a conductive metal film such as zinc or platinum, or carbon is used. The counter electrode 2 is also generally formed on a counter substrate (not shown).
As the material constituting the counter substrate, glass or a plastic film is desirable as in the display electrode 1. When a metal plate such as zinc is used as the counter electrode 2, the counter electrode 2 also serves as a substrate.
Furthermore, when the material constituting the counter electrode 2 includes a material that causes a reaction opposite to the oxidation / reduction reaction caused by the electrochromic composition of the display layer, stable color development and decoloration is possible. That is, when the electrochromic composition is colored by oxidation, the counter electrode 2 causes a reduction reaction, and when the electrochromic composition is colored by reduction, the counter electrode 2 contains a material that causes the oxidation reaction. If it does, the reaction of color development and decoloration in the display layer 5 containing an electrochromic composition will become more stable.

As a material constituting the electrolyte 3, a material in which a supporting salt is dissolved in a solvent is generally used.
Examples of the supporting salt include inorganic ion salts such as alkali metal salts and alkaline earth metal salts, quaternary ammonium salts, acids, and alkali salts. Specifically, LiClO ₄ , LiBF ₄ , LiAsF ₆ , LiPF ₆ , CF ₃ SO ₃ Li, CF ₃ COOLi, KCl, NaClO ₃ , NaCl, NaBF ₄ , NaSCN, KBF ₄ , Mg (ClO ₄ ) ₂ , Mg (BF ₄ ) ₂ or the like can be used.
Examples of the solvent include propylene carbonate, acetonitrile, γ-butyrolactone, ethylene carbonate, sulfolane, dioxolane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,2-dimethoxyethane, 1,2-ethoxymethoxyethane, and polyethylene glycol. , Alcohols are used.
In addition, since it is not particularly limited to a liquid electrolyte in which a supporting salt is dissolved in a solvent, a gel electrolyte or a solid electrolyte such as a polymer electrolyte is also used. For example, there is a solid system such as a perfluorosulfonic acid polymer film. The solution system has an advantage of high ionic conductivity, and the solid system is suitable for producing a highly durable element without deterioration.

When the display element of the present invention is used as a reflective display element, it is desirable to provide a white reflective layer 6 between the display electrode 1 and the counter electrode 2 as shown in FIG. For the white reflective layer 6, it is the simplest production method to disperse white pigment particles in a resin and apply them on the counter electrode 2.
As the white pigment fine particles, particles made of a general metal oxide can be applied, and specific examples include titanium oxide, aluminum oxide, zinc oxide, silicon oxide, cesium oxide, yttrium oxide and the like. Moreover, it can also serve as a white reflective layer by mixing white pigment particles in the polymer electrolyte.

  As a driving method of the display elements 10, 20, and 30, any method may be used as long as an arbitrary voltage and current can be applied. If a passive driving method is used, an inexpensive display element can be manufactured. Further, if the active driving method is used, high-definition and high-speed display can be performed. Active driving can be easily performed by providing an active driving element on the counter substrate.

Hereinafter, the electrochromic compound and the electrochromic composition of the present invention and the display device using the same will be specifically described in Examples, but the present invention is not limited to these Examples. Note that Example 8 is referred to as Reference Example 1 which is not included in the present invention.

[Example 1]
<Synthesis of Electrochromic Compound [Compound (4)]>
<a> Synthesis of Intermediate (4-1) In a 200 ml three-necked flask, 1.309 g (3 mmol) of 2,7-dibromo-9,9-dibutylfluorene, 4- (4,4,5,5-tetra Methyl-1,3,2-dioxaborolan-2-yl) pyridine 2.707 g (13.2 mmol), tetrakistriphenylphosphine palladium 0.694 g (0.6 mmol), Aliquat 336 (manufactured by Aldrich) 0 as phase transfer catalyst After adding 160 g (0.4 mmol) and substituting with argon gas, 45 ml of 1,4-dioxane degassed with argon gas and 22 ml of 1M potassium carbonate aqueous solution were sequentially added and refluxed at 110 ° C. for 1.5 hours. After returning the reaction solution to room temperature, ethyl acetate and water were added. This solution was transferred to a separatory funnel, and the organic layer was washed with water and saturated brine. After adding anhydrous sodium sulfate to this organic layer and stirring at room temperature for 1 hour for dehydration, palladium scavenger silica gel (Aldrich) 3 g) was added and stirred at room temperature for 1 hour to remove residual palladium in the organic layer. After the desiccant and silica gel were filtered off, the solvent was distilled off under reduced pressure. This crude product was purified by silica gel column chromatography (toluene / acetone = 4/1), and the target product (9,9-dibutyl-2,7-bis (4-pyridyl) fluorene) [the following formula (4- Intermediate (4-1)] shown in 1) was obtained. Yield 0.91 g, yield 70%.

<B> Synthesis of Compound (4) In a 25 ml three-necked flask, 0.260 g (0.60 mmol) of 9,9-dibutyl-2,7-bis (4-pyridyl) fluorene obtained above and 4- Bromobenzylphosphonic acid 0.556 g (2.10 mmol) and dimethylformamide 3.0 ml were added and reacted at 90 ° C. for 2 hours. After returning to room temperature, this solution was discharged into a mixed solvent of water / 2-propanol, and then the obtained solid content was dispersed in 2-propanol and then recovered and dried under reduced pressure at 100 ° C. for 2 days. The target product [electrochromic compound (4) represented by the following formula (4)] was thus obtained. Yield 0.38g, Yield 66%

[Example 2]
<Synthesis of Electrochromic Compound [Compound (7)]>
<a> Synthesis of Intermediate (7-1) In a 200 ml three-necked flask, 1.645 g (3 mmol) of 2,7-dibromo-9,9-dioctylfluorene, 4- (4,4,5,5-tetra Methyl-1,3,2-dioxaborolan-2-yl) pyridine 2.707 g (13.2 mmol), tetrakistriphenylphosphine palladium 0.694 g (0.6 mmol), Aliquat 336 (manufactured by Aldrich) 0 as phase transfer catalyst After adding 180 g (0.45 mmol) and substituting with argon gas, 45 ml of tetrahydrofuran degassed with argon gas and 22 ml of 1M potassium carbonate aqueous solution were sequentially added and refluxed at 75 ° C. for 2.5 hours. After returning to room temperature, ethyl acetate and water were added. This solution was transferred to a separatory funnel, and the organic layer was washed with water and saturated brine. After anhydrous sodium sulfate was added to this organic layer and stirred at room temperature for 1 hour for dehydration, palladium scavenger silica gel (Aldrich) was used. 3 g) was added and stirred at room temperature for 1 hour to remove residual palladium in the organic layer. After the desiccant and silica gel were filtered off, the solvent was distilled off under reduced pressure. This crude product was purified by silica gel column chromatography (toluene / acetone = 4/1), and the target product (9,9-dioctyl-2,7-bis (4-pyridyl) fluorene) [following formula (7- Intermediate (7-1)] shown in 1) was obtained. Yield 1.31g, Yield 80%

<B> Synthesis of Compound (7) In a 25 ml three-necked flask, 0.333 g (0.61 mmol) of 9,9-dioctyl-2,7-bis (4-pyridyl) fluorene obtained above and 4- Bromobenzylphosphonic acid 0.556 g (2.10 mmol) and dimethylformamide 3.0 ml were added and reacted at 90 ° C. for 2 hours. After returning to room temperature, this solution was discharged into a mixed solvent of water / methanol, and then the obtained solid content was dispersed in a mixed solvent of methanol / 2-propanol and then recovered and recovered at 100 ° C. at 2 ° C. The desired product [electrochromic compound represented by the following structural formula (7)] was obtained by drying under reduced pressure for days. Yield 0.55g, Yield 84%

[Example 3]
<Synthesis of Electrochromic Compound [Compound (8)]>
<a> Synthesis of Intermediate (8-1) In a 100 ml three-necked flask, 0.548 g (1 mmol) of 2,7-dibromo-9,9-di (2-ethylhexyl) fluorene, 4- (4, 4, 5,02-tetramethyl-1,3,2-dioxaborolan-2-yl) pyridine 0.902 g (4.4 mmol), tetrakistriphenylphosphine palladium 0.231 g (0.2 mmol), Aliquat 336 (as a phase transfer catalyst) (Aldrich) 0.04 g (0.1 mmol) was added, and after replacing with argon gas, 15 ml of tetrahydrofuran degassed with argon gas and 7.2 ml of 1M potassium carbonate aqueous solution were sequentially added, and the mixture was heated at 75 ° C. for 4.5 hours. After refluxing, the reaction solution was allowed to return to room temperature, and then ethyl acetate and water were added. This solution was transferred to a separatory funnel, and the organic layer was washed with water and saturated brine. After anhydrous sodium sulfate was added to this organic layer and stirred at room temperature for 1 hour for dehydration, palladium scavenger silica gel (Aldrich) was used. Product) was added and stirred at room temperature for 1 hour to remove residual palladium in the organic layer. After the desiccant and silica gel were filtered off, the solvent was distilled off under reduced pressure. The crude product was purified by silica gel column chromatography (hexane / ethyl acetate = 1/1) to obtain the desired product (9,9-di (2-ethylhexyl) -2,7-bis (4-pyridyl) fluorene). [Intermediate (8-1) represented by the following formula (8-1)] was obtained. Yield 0.43g, Yield 79%

<B> Synthesis of Compound (8) In a 25 ml three-necked flask, 0.430 g (0.790 mmol) of 9,9-di (2-ethylhexyl) -2,7-bis (4-pyridyl) fluorene obtained above. ), And 0.732 g (2.76 mmol) of 4-bromobenzylphosphonic acid and 3.5 ml of dimethylformamide were added and reacted at 90 ° C. for 3 hours. After returning to room temperature, this solution was discharged into a mixed solvent of water / methanol, and then the obtained solid content was dispersed in water and then recovered and dried under reduced pressure at 100 ° C. for 2 days. An electrochromic compound (8) represented by the following formula (8) was obtained. Yield 0.53g, Yield 62%

[Example 4]
[Production and evaluation of electrochromic display elements]
(A) Formation of display electrode and electrochromic display layer First, a glass substrate having a length and width of 30 mm × 30 mm and a thickness of 1 mm is prepared, and an ITO film is deposited on the upper surface of a 16 mm × 23 mm region by sputtering to a thickness of about 100 nm. The display electrode 1 was formed by forming a film so that When the sheet resistance between the electrode ends of the display electrode 1 was measured, it was about 200Ω.
Next, SP210 (trade name: manufactured by Showa Titanium Co., Ltd.) as a titanium oxide nanoparticle dispersion is applied onto the glass substrate on which the display electrode is formed by spin coating, and oxidized by performing an annealing treatment at 120 ° C. for 15 minutes. A titanium particle film was formed, and subsequently, a solution obtained by dissolving 1 wt% of the electrochromic compound of the compound (4) synthesized in Example 1 in 2,2,3,3-tetrafluoropropanol was used as a coating solution. After applying by spin coating, annealing treatment was performed at 120 ° C. for 10 minutes to form the display layer 5 in which the electrochromic compound was adsorbed on the surface of the titanium oxide particles.
In addition, the structure of the produced electrochromic display element is based on the structure of FIG. 2 (except for the white reflective layer).

(B) Formation of counter electrode Next, apart from the glass substrate, a glass substrate having a length and width of 30 mm × 30 mm and a thickness of 1 mm is prepared, and an ITO film is deposited on the entire upper surface of the glass substrate by a sputtering method to a thickness of about 150 nm. The counter electrode 2 was formed by forming a film so as to be. Furthermore, 25 wt% of 2-ethoxyethyl acetate was added to CH10 (trade name: manufactured by Jujo Chemical Co., Ltd.) as a thermosetting conductive carbon ink on the upper surface of the glass substrate on which the transparent conductive thin film was formed on the entire surface. The solution was applied by spin coating and annealed at 120 ° C. for 15 minutes to form a counter electrode.

(C) Production of electrochromic display device A display substrate and a counter substrate were bonded to each other through a 75 μm spacer to produce a cell. Next, 35 wt% of titanium oxide particles (manufactured by Ishihara Sangyo Co., Ltd.) having a primary particle size of 300 nm are dispersed in a solution in which 20 wt% of tetrabutylammonium perchlorate is dissolved in dimethylsulfoxide to prepare an electrolyte solution. The electrochromic display element (30) of Example 4 was produced by encapsulating in.

<Decoloration test>
The electrochromic display element of Example 4 thus produced was evaluated for color development and decoloration. Evaluation of color development / decoloration was performed by irradiating diffused light using a spectrocolorimeter LCD-5000 manufactured by Otsuka Electronics Co., Ltd.
When a negative electrode was connected to the display electrode 1 of the display element and a positive electrode was connected to the counter electrode 2, and a voltage of 3.0 V was applied for 1 second, the display element developed cyan. Furthermore, when a reverse voltage of −4.5 V (display electrode 1: positive electrode, counter electrode 2: negative electrode) was applied for 2 seconds, the color disappeared completely and the color returned to white. The light absorption spectrum during color development is shown in FIG.
Further, cyan was developed by applying a coloring voltage (display electrode 1: negative electrode, counter electrode 2: positive electrode) at 3.0 V for 1 second, and the colored state was maintained even 300 seconds after the power was turned off. That is, the display element manufactured in Example 4 was capable of cyan coloration and was excellent in image retention.

[Example 5]
The electrochromic display element of Example 5 was produced in the same manner as in Example 4 except that the electrochromic compound of the compound (4) used in Example 4 was used instead of the electrochromic compound of the compound (7). did. As a result of performing a color development / decoloration test in the same manner as in Example 4 using the display element of Example 5, cyan color development was possible and image retention was excellent.

[Example 6]
The electrochromic display element of Example 6 was produced in the same manner as in Example 4 except that the electrochromic compound of the compound (4) used in Example 4 was used instead of the electrochromic compound of the compound (8). did. As a result of performing a color development / decoloration test in the same manner as in Example 4 using the display element of Example 6, cyan color development was possible and image retention was excellent.

[Example 7]
A glass substrate on which a display electrode and an electrochromic display layer are formed in the same manner as in Example 4 is prepared, put in a quartz cell, a platinum electrode as a counter electrode, and an Ag / Ag + electrode as a reference electrode (BAS Corporation: RE- 7) was used, and the inside of the cell was filled with an electrolytic solution in which 20 wt% of tetrabutylammonium perchlorate was dissolved in dimethyl sulfoxide.
The quartz cell was irradiated with deuterium tungsten halogen light (Ocean Optics DH-2000), the transmitted light was detected with a spectrometer (Ocean Optics USB4000), and the absorption spectrum was measured. When a voltage of -1.5 V was applied using a potentiostat (BAS Co., Ltd. ALS-660C), it was confirmed that the color was developed to cyan.

[Example 8]
By reacting the intermediate represented by the formula (7-1) synthesized in Example 2 with ethyl bromide, an electrochromic compound represented by the following structural formula (11) was synthesized.

Next, a water / 2,2,3,3-tetrafluoropropanol (10 wt%) solution was prepared, and 1 wt% of the synthesized compound 11 was dissolved to obtain an electrochromic compound solution.
50 wt% of the electrochromic compound solution was added to an electrolytic solution in which 20 wt% of tetrabutylammonium perchlorate was dissolved in dimethyl sulfoxide, and a glass substrate with SnO ₂ conductive film (AGC: Fabrictech) of 30 mm × 30 mm in length and width was added. An electrochromic display element (10) of Example 8 (see FIG. 1) was fabricated by enclosing in a cell bonded with a display substrate and a counter substrate through a 75 μm spacer.
<Decoloration test>
When a voltage of 3.0 V (electrode on the display substrate: negative electrode, electrode on the counter substrate: positive electrode) was applied to the produced display element for 2 seconds, the display element developed a cyan color. Further, when a reverse voltage of −3.0 V (electrode on display substrate: positive electrode, electrode on counter substrate: negative electrode) was applied for 4 seconds, it completely disappeared and returned to transparency.

[Comparative Example 1]
A comparison was made in the same manner as in Example 4 except that the electrochromic compound of the compound (4) used in Example 4 was replaced with a viologen compound represented by the following structural formula (A) which is a known electrochromic compound. The electrochromic display element of Example 1 was produced.

Using the display element of Comparative Example 1, a color development / decoloration test was conducted in the same manner as in Example 4.
<Decoloration test>
FIG. 4 shows an absorption spectrum in a colored state when a negative electrode is connected to the display electrode 1 of the display element of Comparative Example 1, a positive electrode is connected to the counter electrode 2, and a voltage of 3.0 V is applied. As can be seen from FIG. 4, since the maximum absorption is in the vicinity of 600 nm, the color is blue. That is, cyan coloring cannot be realized.

[Comparative Example 2]
Comparative Example as in Example 4 except that the electrochromic compound of the compound (4) used in Example 4 was changed to a compound represented by the following structural formula (B) which is a known electrochromic compound. 2 electrochromic display elements were produced.

FIG. 4 shows an absorption spectrum in a colored state where a negative electrode is connected to the display electrode 1 of the display element, a positive electrode is connected to the counter electrode 2, and a voltage of 3.0 V is applied. As can be seen from FIG. 4, the maximum absorption in the long wavelength region is in the vicinity of 650 nm, but since there is an absorption band at 500 nm or less, the color is green.
Using the display element of Comparative Example 2, a color development / erasing test was conducted in the same manner as in Example 4.
<Decoloration test>
FIG. 4 shows an absorption spectrum in a colored state when a negative electrode is connected to the display electrode 1 of the display element of Comparative Example 2, a positive electrode is connected to the counter electrode 2, and a voltage of 3.0 V is applied. As can be seen from FIG. 4, the maximum absorption in the long wavelength region is in the vicinity of 650 nm, but since there is an absorption band at 500 nm or less, the color is green. That is, cyan coloring cannot be realized.

From the above evaluation results, it was confirmed that the electrochromic compound of the present invention exhibits sharp light absorption spectrum characteristics during color development and exhibits color development in cyan. A display element having an electrochromic compound of the present invention or an electrochromic composition in which an electrochromic compound is bonded or adsorbed to a conductive or semiconducting nanostructure in a display layer has excellent color development (cyanide) when an electric field is applied. Responsiveness (color development or decoloration) and excellent image retention (maintaining memory).
That is, the electrochromic compound of the present invention is useful as one of the three primary colors necessary for full color, and a display element using this is important as, for example, a rewritable paper-like device technology.

(Reference in FIG. 1)
DESCRIPTION OF SYMBOLS 1 Display electrode 2 Counter electrode 3 Electrolyte 4 Display layer 4a ₃ Functional group (adsorption group)
4a ₁ oxidation / reduction coloring part 4a ₂ spacer part (molecular main skeleton part)
4a Electrochromic compound 10, 20 Display element (reference numeral in FIG. 2)
DESCRIPTION OF SYMBOLS 1 Display electrode 2 Counter electrode 3 Electrolyte 5 Display layer 5a Electrochromic composition 6 White reflection layer 30 Display element

JP 2003-161964 A JP 2004-361514 A Japanese translation of PCT publication No. 2004-520621 Special table 2004-536344 gazette Special table 2001-510590 gazette JP 2003-121883 A JP 2006-106669 A JP 2007-279570 A

Claims (4)

The electrochromic compound represented by the following general formula (A).

[Wherein, R ₁ and R ₂ each independently represents an alkyl group. ] An electrochromic composition comprising the electrochromic compound according to claim 1 bonded or adsorbed to a conductive or semiconducting nanostructure. A display electrode, a counter electrode opposed disposed at a spacing relative to the display electrodes, wherein a two inter-electrode disposed electrolytes, the counter electrode-side surface of the display electrodes, to claim 1 It has a display layer containing the electrochromic compound of description, The display element characterized by the above-mentioned. The display element according to claim 3 , wherein the display layer is the electrochromic composition according to claim 2 .