JPS6224034B2 - - Google Patents

Description

[Detailed description of the invention]

Technical Field The present invention relates to a new electrochromic display device (hereinafter abbreviated as an ECD device), and more specifically to an ECD device using a novel polymer electrochromic material capable of developing a color tone close to colorless. It is. BACKGROUND OF THE INVENTION It is well known that in recent years, liquid crystal display devices have been put into practical use as display devices with low energy consumption and are being used for various purposes. However, liquid crystal display devices have the problem of viewing angle dependence, and further have drawbacks such as poor display clarity, lack of memory performance, and inability to display large areas. As a low-energy display device that compensates for these drawbacks, in recent years, ECD devices that utilize so-called electrochromism, in which light absorption characteristics change depending on voltage application or current, have been actively researched. Electrochromic materials used in ECD devices are broadly classified into inorganic materials and organic materials. For the former, transition metal oxides such as tungsten oxide have been mainly considered, but the colors are limited, or when protons are used as coloring ions, the response speed is fast, but the electrochemical problems of the membrane There are drawbacks such as elution and electrode deterioration. On the other hand, as the latter, viologens, phthalocyanine complexes, etc. are known, but viologens have drawbacks such as precipitation of insoluble substances when used repeatedly. Furthermore, phthalocyanine complexes still have problems in adhesion between the deposited film and the substrate. More recently, polyaniline [A.F. Deias et al., Journal of Electroanalytical Chemistry, Vol. 111, p. 111 (1980) or Yoneyama et al., Vol. 161, p. 419 (1984
)], polypyrrole [A.F. Deias et al.
Vol. 149, p. 101 (1983)], and polythiophene [M.A. Drouy et al., Journal.
Electrochromic, Vol. 44, June issue, pp. C3-595 (1983) or Kindo et al., Japan Journal of Applied Physics, Vol. 22, No. 7, p. L412 (1983), etc. Although it is being considered as a material, it has not yet reached the stage of practical use. In particular, electrochromic materials are desired to have a fast response speed, clear contrast, low power consumption, and excellent color tone. In particular, the ability to produce colorless tones is said to greatly contribute to the expansion of applications, but all of these heteroconjugated polymer materials are colored during the color change process from the oxidized state to the reduced state, and in order to increase contrast, Methods such as using a white background board are being considered, but they have not yet reached the stage of completion. Purpose of the Invention In the process of various studies on the electrochemical behavior of polymers having an isothianaphthene structure, the present inventors discovered that the above polymer has a fast response speed and a novel color tone that is almost colorless in an oxidized state. The present invention was achieved by discovering that it is an electrochromic material. It is truly surprising that this has been achieved, especially since electrochromic materials that provide an almost colorless tone are hitherto unknown. Structure of the Invention The ECD device of the present invention uses a conductive polymer thin film formed on a conductive transparent substrate as a display substrate,
A counter electrode is placed on this via a liquid electrolyte.
The ECD device is characterized in that the conductive polymer thin film is a reversibly oxidizable or reducible polymer having an isothianaphthene structure. The term "liquid electrolyte" as used herein means a supporting electrolyte dispersed or dissolved in a solvent. Detailed Description of the Invention The conductive polymer thin film to be the electrochromic layer according to the present invention has the general formula () (In the formula, R ¹ and R ² represent hydrogen or a hydrocarbon having 1 to 5 carbon atoms, X represents an anion, and y represents the ratio of anion per unit of the isothianaphthene structure. It is a reversibly oxidizable or reducible polymer having an isothianaphthene structure represented by the following general formula (), where n represents the degree of polymerization and is preferably a number from 5 to 500. It can be obtained by electrochemically polymerizing isothianaphthene compounds. (In the formula, R ¹ and R ² represent hydrogen or a hydrocarbon group having 1 to 5 carbon atoms.) Specific examples of the isothianaphthene compound represented by the general formula () include 1,3-isothianaphthene, 5-methyl-1,3-isothianaphthene,
5,6-dimethylisothianaphthene, 5-ethyl-1,3-isothianaphthene, 5-methyl-6-
Examples include ethyl-1,3-isothianaphthene. As a method for electrochemically polymerizing the above-mentioned isothianaphthene compound, a method for electrochemically polymerizing ordinary thiophene, pyrrole, etc. [for example, Solid State Communication Vol. 46, 5
No. 389 (1983)], and both the constant potential method and the constant current method can be used, but by using a conductive transparent substrate as the sample electrode, it is possible to It is desirable to form a coalesced thin film. The conductive transparent substrate used in the present invention can be easily obtained as a commercially available product made by depositing indium tin oxide, tin oxide, platinum, etc. on a transparent insulator such as glass, polyester, or film by a method such as sputtering. I can use things. The film thickness of the polymer obtained by electrochemical polymerization is 0.03 to 30 μm, preferably 0.05 to 22 μm.
m, more preferably 0.1 to 10 μm, and the film thickness can be controlled by the amount of current applied during electrochemical polymerization. If the film thickness is less than 0.03 μm, the contrast will not be clear and the value as a display material will be substantially lost. On the other hand, if it exceeds 30 μm, the contrast becomes clearer, but it is not preferable from the viewpoint of film strength or response speed. An ECD device is made by assembling the polymer thus obtained via a counter electrode and a liquid electrolyte, and the liquid electrolyte used is one in which a supporting electrolyte is dispersed or dissolved in a solvent. Supporting electrolytes used in the present invention include (i) aqueous electrolytes such as PF ^- ₆ , SbF ^- ₆ , AsF ^- ₆ , and SbCl ^- ₆ ;
halide anions of group elements, halide anions of group a elements such as BF ^- ₄ , I ^- (I ^- ₃ ),
Halogen anions such as Br ^- , Cl ^- , anions such as perchlorate anions such as ClO ^- ₄ (general formula ()
X) and (ii) alkali metal ions such as Li ⁺ , Na ⁺ , K ^{+ ,} quaternary ammonium ions such as R ₄ N ⁺ (R is a hydrocarbon group having 1 to 20 carbon atoms), (C ₆ H ₅ ) _4P ⁺
It is possible to use combinations with phosphonium ions such as the following, but it goes without saying that the present invention is not necessarily limited to these. Specific examples of supporting electrolytes obtained by combining the above-mentioned anions (X) and cations include LiPF ₆ , LiSbF ₆ , LiAsF ₆ , LiClO ₄ , NaI,
_NaPF6 , _NaSbF6 , _NaAsF6 , _NaClO4 , KI,
KPF ₆ , KSbF ₆ , KAsF ₆ , KClO ₄ , [(n-
Bu) ₄ N] ⁺・(AsF ₆ ) ^- , [(n-Bu) ₄ N] ⁺・(PF ₆ ) ^-
,
[(n-Bu) _4N ⁺・ClO ⁻ ₄ , _LiAlCl4 , _LiBF4 ,
(C ₆ H ₅ ) ₄ P・BF ₄ , (C ₆ H ₅ ) ₄ P・AsF ₆ , (C ₆ H ₅ ) ₄ P・
Examples include, but are not limited to, ClO ₄ . These supporting electrolytes may be used alone or in combination of two or more types as required. Anion (X) other than the above is an HF ^- ₂ anion, and cation other than the above is a pyrylium or pyridinium cation represented by the following formula (): (In the formula, Z is an oxygen atom or a nitrogen atom, R' is a hydrogen atom, an alkyl group having 1 to 15 carbon atoms, an aryl group having 6 to 15 carbon atoms, and R'' is a halogen atom or a carbon number 1 -10 alkyl group, aryl group having 6 to 15 carbon atoms, m is 0 when X is an oxygen atom, and 1 when X is a nitrogen atom.
p is 0 or 1-5. ) or a carbonium cation represented by the following formula () or (): and [In the above formula, R ³ , R ⁴ and R ⁵ are hydrogen atoms (however, R ³ , R ⁴ and R ⁵ are never hydrogen atoms at the same time), an alkyl group having 1 to 15 carbon atoms, allyl group, an aryl group having 6 to 15 carbon atoms or -OR ⁷ group,
However, R ⁷ represents an alkyl group having 1 to 10 carbon atoms or an aryl group having 6 to 15 carbon atoms, and R ⁶ represents a hydrogen atom, an alkyl group having 1 to 15 carbon atoms, or an aryl group having 6 to 15 carbon atoms.
~15 aryl groups. ]. The HF ^- ₂ anion used usually has the following general formula (), () or (): R' ₄ N·HF ₂ () M·HR ² () [However, in the above formula, R' and R'' are a hydrogen atom, an alkyl group having 1 to 15 carbon atoms, an aryl group having 6 to 15 carbon atoms, and R is an alkyl group having 1 to 10 carbon atoms, a carbon A compound (hydrofluoride salt) represented by a number 6 to 15 aryl group, Z is an oxygen atom or nitrogen atom, q is 0 or a positive integer of 5 or less, M is an alkali metal] It can be obtained by dissolving it in a suitable organic solvent using it as a supporting electrolyte.Specific examples of the compounds represented by the above formulas (), () and () include H ₄ N・HF ₂ , Bu ₄・
HF ₂ , Na・HF ₂ , K・HF ₂ , Li・HF ₂ and

[Formula] can be given. The pyrylium or pyridinium cation represented by the above formula () is a cation represented by the formula () and ClO ^- ₄ , BF ^- ₄ , AlCl ^- ₄ , FeCl ^- ₄ ,
SnCl ^- ₅ , PF ^- ₆ , PCl ^- ₆ , SbF ^- ₆ , AsF ^- ₆ , _CF3SO
^-3 _,
It can be obtained by dissolving in a suitable organic solvent using a salt with anion (X) such as HF ^- ₂ as a supporting electrolyte. Examples of such salts include

【formula】

【formula】

【formula】

【formula】

【formula】

【formula】

【formula】

【formula】

【formula】

[Formula] etc. can be given. Specific examples of carbonium cations represented by the above formula () or () are (C ₆ H ₅ ) ₃ C ⁺ , (CH ₃ ) ₃ C ⁺ ,

【formula】

[Formula] can be given. These carbonium cations can be obtained by dissolving or dispersing a salt (carbonium salt) of them and anion (X) in a suitable organic solvent as a supporting electrolyte. Representative examples of the anion [X] used here include BF ^- ₄ , AlCl ^- ₄ ,
AlBr ₃ Cl ^- , FeCl ^- ₄ , SnCl ^- ₃ , PF ^- ₆ , PCl ^- ₆ ,
SbCl ^- ₆ , SbF ^- ₆ , ClO ^- ₄ , CF ₃ SO ^- _3, etc. can be mentioned, and specific examples of carbonium salts include (C ₆ H ₅ ) ₃ C・BF ₄ , (CH ₃ ) ₃ C・BF ₄ ,
Examples include HCO・AlCl ₄ , HCO・BF ₄ , C ₆ H ₅ CO・SnCl ₅ and the like. As the solvent of the present invention, either an aqueous solution or a non-aqueous solution can be used, but preferably the supporting electrolyte is dissolved in a non-aqueous organic solvent. The organic solvent mentioned here is preferably one that is aprotic and has a high dielectric constant. For example, ethers, ketones, nitriles, amines, amides, sulfur compounds, phosphate ester compounds,
Phosphite compounds, borate compounds, chlorinated hydrocarbons, esters, carbonates, nitro compounds, etc. can be used, but among these, ethers, ketones, nitriles, phosphoric acid Preferred are ester compounds, phosphite compounds, boric acid ester compounds, chlorinated hydrocarbons, and carbonates. Representative examples of these include tetrahydrofuran, 2-
Methyltetrahydrofuran, 1,4-dioxane, monoglyme, acetonitrile, propionitrile, 4-methyl-2-pentanone, butyronitrile, valeronitrile, benzonitrile, 1,2
-dichloroethane, γ-butyrolactone, valerolactone, dimethoxyethane, methylformate, propylene carbonate, ethylene carbonate, dimethylformamide, dimethyl sulfoxide, dimethylthioformamide, ethyl phosphate, methyl phosphate, ethyl phosphite, phosphorous acid Methyl, sulfolane, 3-methylsulfolane, etc. can be mentioned. Among these, nitriles or carbonates are particularly preferred in order to increase response speed. These organic solvents may be used alone or as a mixed solvent of two or more. Depending on the type of ECD device used or the type of electrode used, oxygen, water, protic solvents, etc. in these solvents may
Because it may deteriorate the characteristics of the ECD device,
In that case, it is preferable to purify according to a conventional method. In addition, in the ECD device of the present invention, polyethylene oxide and NaI are used in addition to the above-mentioned electrolyte.
It is also possible to use a highly ionic conductive organic solid electrolyte or supporting electrolyte made of NaSCN or the like simply dispersed in an organic solvent. The concentration of the supporting electrolyte used in the ECD device of the present invention cannot be unconditionally defined because it varies depending on the type of organic solvent used, the current value at the time of application, the voltage value, the operating temperature, the type of supporting electrolyte, etc. . The liquid electrolyte may be homogeneous or heterogeneous, but it is usually in the range of 0.001 to 10 mol/. The distance between the polymer conductive thin film and the counter electrode in the present invention varies depending on the type of solvent used, the type and concentration of the supporting electrolyte, the current value and voltage value at the time of application, the display area of the ECD device, etc. It is not possible to specify 0.05 to 5.
Preferably, it is mm. Further, the counter electrode used in the present invention may be made of various materials depending on the purpose. That is, when using transmitted light as a display device, it is preferable to use, for example, a conductive transparent material as described above as the counter electrode. On the other hand, when reflected light is used, it is also possible to use an opaque conductive material as the counter electrode, so for example, metal foil such as nickel or platinum or gauze can also be used. Also, to provide an almost colorless tone, a variety of tones can be selected as the background plate. In this way, the present invention can obtain
ECD devices can be applied to a wide range of applications due to their versatility in terms of materials. EXAMPLES The present invention will be explained in more detail with reference to Examples below, but it goes without saying that the technical scope of the present invention is not limited by these Examples.
In addition, in the following example, the NMR spectrum is
Varian EM-360A with TMS as internal standard
¹ H-NMR was measured using a spectrometer, and infrared absorption spectra were measured using a model 281 device manufactured by PerkinElmer. Example 1 Production of polyisothianaphthene by treating 1,3-dihydroisothianaphthene-2-oxide in concentrated sulfuric acid (a) Synthesis of 1,3-dihydroisothianaphthene-2-oxide Lithium triethylboron Hydride 1
3.21 g (0.1 mol) of powdered sulfur in a Diurene flask at room temperature was added to 200 ml of the mol/solution under a nitrogen stream. A reaction occurred immediately, the sulfur powder dissolved and a yellow suspension was obtained. When this solution was exposed to a small amount of air, it turned into a pale yellow transparent solution. Separately, 26.4 g of o-xylylene dibromide was placed in a 2-four-necked flask equipped with a dropping funnel, stirrer, thermometer, and nitrogen inlet under a nitrogen atmosphere.
(0.1 mol) was dissolved in 1 mol of anhydrous tetrahydrofuran, and while stirring, 1.5 mol of the above tetrahydrofuran solution of lithium sulfide was added at room temperature.
It dripped over time. Thereafter, tetrahydrofuran was distilled off under reduced pressure, and the residue was further distilled to obtain 10.9 g (yield: 80%) of colorless 1,3-dihydroisothianaphthene, having a temperature of 74 to 76°C/3 mmHg. The infrared absorption spectrum of this product is 3060,
Absorption based on phenyl groups at 3026, 1582, and 1485 cm ^-1 , absorption based on methylene groups at 2910, 2840, and 1450 cm ^-1 , in-plane bending absorption of 1,2-substituted phenyl at 1195 cm ^-1 , and o at 760 cm ^-1 -Substituted phenyl absorption and sulfide absorption at 740 cm ^-1 .
Also, nuclear magnetic resonance spectra ( ¹ H-NMR) in deuterated chloroform using TMS as an internal standard.
The analysis results were as follows. 4.22 (S, 4H), 7.20 (S, 4H) This compound was extremely unstable and changed from yellow to black even when stored in a tightly sealed container protected from light. Next, the obtained 1,3-dihydroisothianaphthene was added to sodium metaiodate prepared in advance.
It was added to 450 ml of 50% methanol aqueous solution in which 18.6 g (0.086 mol) was dissolved, and stirred at room temperature for 12 hours. The generated precipitate was filtered off, and the residue was washed with 50 ml of methanol and combined with the mother liquor. The filtrate was concentrated under reduced pressure, and the resulting yellow-white solid was recrystallized from ethyl acetate/cyclohexane to obtain slightly yellowish crystals. The melting point of this crystal was 87-89°C. When the obtained crystals were further recrystallized from ethyl acetate/cyclohexane, they showed a melting point of 90-91°C. In the infrared absorption spectrum of this crystal, in addition to the absorption of isothianaphthene, strong absorption of sulfoxide was observed at 1035 cm ^-1 , and the absorption of sulfoxide at 740 cm ^-1 disappeared. In addition, ¹ H− in deuterated chloroform with TMS as an internal standard.
The NMR spectrum was as follows. 4.65 (S, 4H), 7.20 (S, 4H) The results of elemental analysis of the above crystals were as follows. Actual value
C: 63.08% H: 5.15% S: 20.87% Calculated values (as C ₈ H ₈ SO) C: 63.16% H: 5.26% S: 21.05% Example 2 Polydihydroisothia obtained by cationic polymerization of isothianaphthene Production of polyisothianaphthene by oxidizing naphthene using an oxidizing agent (a) Isothianaphthene (in the general formula R ¹ = R ² =
Synthesis of H) 300 mg of 1,3-dihydroisothianaphthene-2-oxide synthesized based on Example 1(a)
(1.97 mmol) and 450 mg (4.41 mmol) of neutral alumina were thoroughly ground and mixed in a mortar, placed in a sublimator, and heated under reduced pressure on an oil bath. 110℃/
At 20 mmHg, 250 mg (1.87 mmol) of white needle-like crystals of isothianaphthene were obtained at the bottom of the sublimator cooling section. This monomer was immediately purified and degassed.
The mixture was dissolved in 1 ml of methylene chloride, 10 mg of trifluoroacetic acid was added at room temperature, and the mixture was left overnight. reaction solution
Pouring into 50 ml of methanol gave a white precipitate. This polymer was soluble in chloroform, chlorobenzene, tetrahydrofuran, and N.N-dimethylformamide. The infrared absorption spectrum of the polymer is shown in FIG. 1, and ^{the 1} H-NMR spectrum is shown in FIG. 2. A gel permeation chromatograph (Varian 5000) of a solution of this polymer in tetrahydrofuran confirmed that the molecular weight was 2000 in terms of polystyrene. The electrical conductivity (σ _RT ) of this polymer at room temperature was measured using a 4-terminal conductivity meter, and it was found to be less than σ _RT =10 ⁻⁸ s/cm. The results of elemental analysis were as follows. Actual value
C: 71.27% H: 4.54% S: 23.96% Calculated values (as (C ₈ H ₆ S) n) C: 71.64% H: 4.48% S: 23.88% In the above method, methanesulfone is used instead of trifluoroacetic acid. When an acid was used as a polymerization initiator, a polymer was obtained in the same manner, and its infrared absorption spectrum completely matched that shown in FIG. When these polymers were dissolved in 5 ml of chlorobenzene and treated with twice the molar amount of chloranil, a black precipitate was formed. The electrical conductivity σ _RT of this polymer at room temperature is 9×10 ^-2 s/cm, and the electrical conductivity of the iodine-doped product is σ _RT =9×
It was 10 ^-1 s/cm. The infrared absorption spectrum of this product was as shown in FIG. Even when the doped polymer was left in the air at room temperature for one week, there was no change in its electrical conductivity. When 1.1 times the amount of N-chlorosuccinimide was used instead of chloranil and 5 ml of chloroform was used, a black precipitate was obtained that showed exactly the same infrared absorption spectrum as shown in FIG. 3. The conductivity σ _RT of this polymer is 2.6×10 ^-1 s/cm
It was hot. Example 3 0.0788 mol/ _{1,3 -} isothianaphthene monomer (R ¹ ₌ R ² =
A solution containing H compound) was used as the electrolyte, and a glass plate on which indium tin oxide was deposited was used as the sample electrode
2m with Al plate as counter electrode and Li/Li ⁺ as reference electrode.
After electrochemical polymerization at room temperature for 20 minutes at a current density of A/cm ² , an electrochemically neutral deep blue polymer was obtained on the indium tin oxide deposited glass plate of the positive electrode. The film thickness after washing with acetonitrile and drying was 10 μm. This material was immersed in a THF solution containing 0.53 mol/LiClO ₄ and the dependence of optical absorption on applied voltage was observed using Li as a counter electrode. The results are shown in FIG. In other words, as seen in this figure, the polymer
It showed a blue color at 2.50V (versus Li), and changed to a transparent light green color at 3.50V. This change was found to be reversible. Cyclic portanograms were then measured at +1.0 V to -0.7 V (vs. standard calomel electrode) using (C ₄ H ₉ ) ₄ NClO ₄ in acetonitrile as the electrolyte.
The results are shown in FIG. In the range of +0.6V to -0.7V, the polymer film is dark blue;
In the 1.0V range, the color changed to a highly transparent light green color. Using this result, an ECD device as shown in FIG. 6 was fabricated, and a propylene carbonate solution of an electrolyte containing 0.53 mol/LiBF ₄ was sealed as a liquid electrolyte. When we tried a life test by applying a square wave of +0.8V to -0.4V with a cycle of 1Hz, we found that 2×
10 No deterioration of the electrochromic material was observed even after ^four coloring/decoloring tests.

[Brief explanation of the drawing]

FIG. 1 is an infrared absorption spectrum diagram of the polymer produced in Example 2, and FIG. 2 is an NMR spectrum diagram of the polymer produced in Example 2. FIG. 3 is an infrared absorption spectrum diagram of the first polymer produced in Example 2 after being treated with chloranil. FIG. 4 is a diagram showing the dependence of optical absorption on applied voltage when the conductive polymer film of Example 3 is immersed in a THF solution of 0.53 mol/LiClO ₄ and Li is used as a counter electrode. The figure is a cyclic portanogram of the polymer conductive membrane of Example 3 measured at +1.0V to -0.7V (vs. standard calomel electrode) when acetonitrile (C ₄ H ₉ ) ₄ NClO ₂ was used as the electrolyte. be. FIG. 6 is a schematic cross-sectional view showing an embodiment of the ECD device according to the present invention, in which 1 is a transparent glass substrate, 2 is a display electrode, 3 is an electrochromic material, 4 is a liquid electrolyte, and 5 is an opposing An electrode, 6 a protective layer, and 7 a lead wire.

Claims (1)

[Scope of Claims] 1. An electrochromic display device in which a conductive polymer thin film formed on a conductive transparent substrate is used as a display substrate, and a counter electrode is disposed thereon via a liquid electrolyte. The conductive thin film has the following general formula (): (In the formula, R ¹ and R ² represent hydrogen or a hydrocarbon having 1 to 5 carbon atoms, X represents an anion, and y represents the proportion of anion per unit of the isothianaphthene structure of 0 to 0.40. (where n represents the degree of polymerization, preferably a number from 5 to 500). Display device.