Polyisothianaphtene, a new conducting polymer

A polymer having an isothianaphthene structure represented by the formula (Ia) and/or Ib): ##STR1## wherein R.sup.1 and R.sup.2 each represents a hydrogen atom or a hydrocarbon residue having 1 to 5 carbon atoms such as methyl, methoxy and thiomethyl, with the proviso that R.sup.1 and R.sup.2 may link together to form, along with the benzene ring, a fused ring which is naphthalene; X is sulfur, selenium or tellurium; Y.sup.- represents an anion of an electrolyte; z represents a number from 0.01 to 1 showing a ratio of the anion per mol of a monomer; and n represents a number of from 5 to 500 showing a degree of polymerization. An electrochromic display wherein a high molecular weight conductive membrane formed on a conductive transparent base is used as a display base and an opposing electrode is arranged thereunder via a liquid electrolyte, which is characterized in that said high molecular weight conductive membrane is a polymer having an isothianaphthene structure and capable of being reversibly oxidized or reduced.

BACKGROUND OF THE INVENTION 
With the latest remarkable developments in lightening, thinning or 
miniaturization of electric and electronic instruments, not only 
lightening, thinning or miniaturization of various conductive materials 
used therein but also new development of these materials per se have been 
desired. 
Various sulfur-containing heterocyclic polymers are known including 
polymers from thiophene, U.S. Pat. No. 2,552,796 and U.S. Pat. No. 
2,658,902; polymers from dibenzothiophene, U.S. Pat. No. 3,585,163; 
polymers from vinyl bithiophene, U.S. Pat. No. 3,615,384; polymers from 
various substituted thiophenes, U.S. Pat. No. 3,725,362; polymers from 
2-bromo-8-hydroxy-5,5-dioxodibenzothiophene, U.S. Pat. No. 3,775,368; and 
polymers from tetrathiapentalene, U.S. Pat. No. 4,111,857. 
Within the rapidly expanding field of polymeric conductors ("Proceedings of 
the International Conference on the Physics and Chemistry of Polymeric 
Conductors", J. Physique. Colloque, 1983, C-3), the poly(heterocycles) 
have received attention because they are easily prepared in film form and 
are considerably more stable to atmospheric exposure than poly(acetylene) 
or poly(phenylene). For use in stabilizing a semiconductor surface, see R. 
Noufi et al., J. Amer. Chem. Soc., 1981, Vol. 183, 184 and references 
therein. A further extension of this work is our recent entry into the 
study of poly(thiophene). 
Extensive investigations on new conductive high polymers have been 
conducted. For example, polyacetylenes are under investigation for their 
possible availability as electrode materials of secondary batteries since 
they show excellent conductivities as high as 10.sup.2 to 10.sup.3 s/cm by 
doping iodine or arsenic pentafluoride (cf. Synthetic Metals, Vol. 1, No. 
2, 101 (1979/1980)), and excellent charge-discharge characteristics. 
Further, use of polyacetylenes as materials for solar batteries is also 
under investigation because of their light absorption characteristics 
close to those of sun light. However, the polyacetylenes are 
disadvantageous in that they are per se susceptible to oxidation and doped 
polyacetylenes are extremely sensitive to humidity. 
Polythiophenes are studied not only as conductive materials or as battery 
electrode materials because of their specific electronic structure having 
a conjugated structure similar to that of cis-form polyacetylenes and 
containing a sulfur atom, but also as electrochromic materials making use 
of color changes in a doped state. For example, A. M. Druy, et al reported 
that 2,2'-bithienyl is electrochemically polymerized to form a polymer 
having a color which reversibly varies from blue in an oxidized state to 
red in a reduced state and such a polymer is useful as an electrochromic 
material making use of the reversibility of the color change [cf. Journal 
de Physique, Vol. 44, No. 6, C3-595 (1983)]. 
In the light of the above-described problems, the present inventors have 
conducted extensive investigations and, as a result, found that a polymer 
having an isothianaphthene structure is a very stable compound even in air 
and capable of reversibly varying its color in the course of oxidation or 
reduction in such a stable manner as sufficient to allow repeated use 
thereof and it is a novel polymer that can easily show conductivities 
higher than 10.sup.-2 s/cm upon doping general dopants and, thus 
accomplished the present invention. 
According to the present invention, we have now synthesized 
poly(isothianaphthene), a polymer of a "nonclassical" thiophene (M. P. 
Cava et al., Acc. Chem. Res., 1975, Vol. 8, 139). While not bound by any 
theory, we believe that poly(isothianaphthene) exhibits higher stability 
(and perhaps conductivity) than poly(thiophene) because the resonance 
contributors 1c and 1d shown in FIG. A are important in the stabilization 
of open shell species (1c) and delocalization along the backbone (1d) is 
responsible for high electrical conductivity. 
##STR2## 
The analogous resonance structure (particularly the analog of ld) would not 
be expected to be as important contributors to the electronic structure of 
poly(thiophene) as they are in the case of poly(isothianaphthene) because 
of the overwhelming gain in stability resulting from incorporation of the 
3,4 bond of thiophene into a benzene ring. 
In the case of the preparation of poly(thiophene), the two simplest methods 
are anodic polymerization of pure thiophene (A. Diaz, Chem. Scripta, 1981, 
Vol. 17, 145; G. Tourillon et al., J. Electroanal. Chem., 1982, Vol. 135, 
173; C. Kossmehl et al., Makromol. Chem. Rapid Commun., 1981, Vol. 2, 551; 
J. Bargon, IBM, J. of Res. and Dev., 1983, Vol. 27, 330; K. Kaneto et al., 
J Chem. Soc. Chem. Com., 1983, 382), and chemical coupling of 
2,5-dihalothiophenes (M. Kobayashi et al., Synthetic Metals, 1984, Vol. 9, 
77; T. Yamamoto et al., J. Polym. Sci., Polym. Lett., 1980, Vol. 18, 9; J. 
Lin et al., J. Polym. Sci., Polym. Chem. Edition, 1980, Vol. 18, 2869). 
The former procedure provides improved materials if 2,2-dithienyl is 
employed as starting material (M. A. Druy, J. Physique. Colloque, 1983, 
Vol. C-3, 595) and the electrolysis is carried out at relatively low 
applied voltages ( .about.3.5 V). From a practical point of view, the 
anodic polymerization is the more desirable; it is simple and the product 
appears in the form of a relatively tough, blue-black film. The chemically 
coupled product is of more academic interest since it is crystalline and 
its numberaverage molecular weight is known but it is invariably produced 
in powder form. 
We have found that the most desirable approach to poly(isothianaphthene) is 
through the electrochemical coupling of isothianaphthene. (Monomer 
prepared according to J. A. Gadysz et al., Tetrahedron, 1979, Vol. 35, 
2239; M. P. Cava et al., J. Amer. Chem. Soc., 1959, Vol. 81, 4266; M. P. 
Cava et al., J. Org. Chem., 1971, Vol. 36, 3932. 
In this patent, we present procedures (electrochemical and chemical) for 
the preparation of poly(isothianaphthene). As will be shown below, 
electrochemical polymerization to yield the desired unsaturated polymer is 
possible only under rather specific conditions. 
As is well known, liquid crystal display devices have recently been 
developed as display devices requiring low energy and been widely used in 
various applications. However, liquid crystal devices have a problem of 
dependence on a visual angle and also are disadvantageous in that the 
display is poor in sharpness; no memory function is provided; display 
cannot be obtained over a large surface area; and the like. In order to 
eliminate these disadvantages, studies have extensively been conducted on 
ECD devices of low energy type making use of the so-called electrochromism 
in which light absorption characteristics vary due to application of 
voltage or electric current. Electrochromic materials which can be used in 
the ECD devices are classified into inorganic materials and organic 
materials. The inorganic materials that are considered usable mainly 
include oxides of transition metals, a specific example is wolfram oxide, 
but they are limited in developable colors and also cause electrochemical 
elution of the membrane or deterioration of electrodes when protons are 
used as color-forming ions, although their response speeds are high. On 
the other hand, the organic materials include viologen dyes, 
phthalocyanine complexes, etc. However, the viologen dyes are 
disadvantageous in that repeated use thereof results in precipitation of 
insoluble substances, and the phthalocyanine complexes have a pending 
problem of adhesiveness between a vacuum-evaporated membrane and a base 
plate. 
In addition, electrochromic materials which have recently been proposed 
include polyanilines as disclosed in A. F. Diaz, et al., Journal of 
Electro-Analytical Chemistry, Vol. 111, 111 (1980) or Yoneyama, et al., 
ibid., Vol. 161, 419 (1984); polypyrroles as disclosed in A. F. Diaz, et 
al., ibid., Vol. 101 (1983) and polythiophenes as disclosed in M. A. Druy, 
et al., Journal de Physique, Vol. 44, June, page C3-595 (1983) or Kaneto 
et al., Japan Journal of Applied Physics, Vol. 23, No. 7, page L412 
(1983), but none of them has not yet been put into practical use. In 
particular, electrochromic materials are required to exhibit rapid 
response, provide high contrast, consume low power, develop excellent 
color tones and the like. Furthermore, an electrochromic material capable 
of developing a colorless tone will greatly contribute to broadening the 
utility of the device. However, any of these hetero-conjugated type high 
molecular weight materials are colored in the course of conversion from an 
oxidized state into a reduced state. Methods for increasing contrast by, 
for example, employing a white background plate, have been attacked but 
still not reached completion. 
SUMMARY OF THE INVENTION 
Briefly, the present invention comprises a polymer having an 
isothianaphthene structure represented by the formula (Ia) and/or (Ib): 
##STR3## 
wherein R.sub.l and R.sub.2 each represents a hydrogen atom or a 
hydrocarbon residue having 1 to 5 carbon atoms such as methyl, methoxy and 
thiomethyl, with the proviso that R.sub.l and R.sup.2 may link together to 
form, along with the benzene ring, a fused ring which is naphthalene; X is 
sulfur, selenium or tellurium; Y.sup.- represents an anion of an 
electrolyte; z represents a number from 0.01 to 1 showing a ratio of the 
anion per mol of a monomer; and n represents a number of from 5 to 500 
showing a degree of polymerization. 
An electrochromic display wherein a high molecular weight conductive 
membrane formed on a conductive transparent base is used as a display base 
and an opposing electrode is arranged thereunder via a liquid electrolyte, 
which is characterized in that said high molecular weight conductive 
membrane is a polymer having an isothianaphthene structure and capable of 
being reversibly oxidized or reduced. 
The above-described polymer can be used in the electric and electronic 
fields as electrodes or electrochromic display elements, or for the 
production of solar batteries, electric splicing, fixing and conversion 
devices of electromagnetic wires, or as reversible oxidation-reduction 
systems. 
The polymers according to the present invention can easily be synthesized 
by various polymerization methods. 
Poly(isothianaphthene) and related polymers are prepared by several 
different approaches. Electrochemical polymerization of isothianaphthene 
is strongly electrolyte dependent. Nucleophilic anions (Brhu -, Cl.sup.-) 
allow formation of poly(isothianaphthene). The latter, either in a 
Bronsted acid (HSO.sub.4.nH.sub.2 O) doped form or chloride doped form is 
a better conductor than polythiophene by ca. one order of magnitude. 
For example, 1,3-dihydroisothianaphthene-2-oxide or a derivative thereof 
represented by the formula (IIa): 
##STR4## 
is reacted in a solvent having a dehydrating and oxidizing effect, such as 
concentrated sulfuric acid, to form the desired polymer. 
Further, the desired polymer can also be obtained by subjecting 
isothianaphthene or a derivative thereof represented by the formula (IIb): 
##STR5## 
which is obtainable, for example, by dehydration and sublimation of the 
compound represented by the formula (IIa) on alumina, to (i) 
electrochemical polymerization in an aprotic solvent in the presence of an 
electrolyte; (ii) cationic polymerization in the presence or absence of a 
solvent, followed by reacting the resulting dihydro type polymer with an 
oxidizing agent for dehydrogenation; (iii) oxidative polymerization; or a 
like method. 
Solvents which can be used in the above-described polymerization of 
monomers are not particularly restricted and can properly be selected 
according to the method of polymerization. In general, in the case when 
the isothianaphthene or its derivative represented by the formula (IIb) is 
electrochemically polymerized in the presence of an electrolyte, aprotic 
solvents, such as acctonitrile, benzonitrile, propionitrile, dioxane, 
tetrahydrofuran, sulforan, propylene carbonate, etc., can be used. In the 
case when isothianaphthene or its derivative of the formula (IIb) is 
cationically polymerized, solvents usable include dichloromethane, 
chloroform, carbon tetrachloride, dichloroethane, tetrafluoroethane, 
nitromethane, nitroethane, nitrobenzene, carbon disulfide, etc. In the 
case when the dihydroisothianaphthene-2-oxide or its derivative of the 
formula (IIa) is dehydration-polymerization, solvents such as concentrated 
sulfuric acid and polyphosphoric acid can be used. Further, when the 
isothianaphthene or its derivative of the formula (IIb) is subjected to 
oxidative addition polymerization, a combination of the solvents used in 
the cationic polymerization and Friedel-Crafts catalysts can be used. 
Polymerizaton temperatures which can be used in the above-described 
polymerization of monomers can be determined according to the respective 
polumerization methods and are not particularly critical, but it is 
generally desirable to carry out the polymerization at temperatures 
ranging from -80.degree. to 200.degree. C. The poylmerization time can be 
determined depending on the method and temperature of polymerization, the 
structure of monomers, etc., but it is usuaUy preferable to conduct 
polymerization for a period of from O.25 hours to 200 hours. The 
above-described monomer compounds represented by the formulae (IIa) and 
(IIb) can be synthesized according to known processes, for example the 
processes described in M. P. Cava, et al., Journal of American Chemical 
Society VoL 81 4266 (1959) and M. P. Cava, et al., Journal of Organic 
Chemistry, Vol. 36, No. 25, 3932 (1971). Further, in order to increase 
yields of 1,3-dihydroisothianaphthene, a method of using solubized lithium 
sulfide which can be obtained by reacting lithium triethyl borohydride 
with sulfur is proposed in J. A. Gradysz, et al., Tetrahedron Letters, 
Vol. 35, 2329 (1979). 
The invention also includes the preparation of this novel polymer. 
It is an object of our invention to provide a novel polymer. 
It is a more particular object of this invention to provide a novel 
electrically conductive polymer. 
It is also an object of this invention to provide novel means for obtaining 
novel polyisothianaphthene-type polymers. 
These and other objects and advantages of our invention will be apparent 
from the more detailed description which follows.

The thus obtained polymers according to the present invention have an 
entirely novel structure, and can not only exhibit markedly high 
conductivity through coping but also repeatedly perform electrochemical 
oxidation-reduction reaction while assuming inherent colors in the 
respective states. Moreover, the polyisothianaphthene of this invention is 
a particularly interesting polymer, for its transparency is not lost even 
in a further oxidized state. Therefore, the polymers having an 
isothianaphthene structure according to the present invention are greatly 
useful in the electric and electronic industries, for example, as 
electrodes, electrochromic display elements, solar batteries, electric 
splicing, fixing and conversion devices of electromagnetic wires as well 
as reversible oxidation-reduction systems. 
The present invention will now be illustrated in greater detail by way of 
examples, but it should be understood that these examples are not limiting 
the scope of the present invention. In the following examples, nuclear 
magnetic resonance spectra (.sup.l H-NMR) were measured by means of a 
spectrophotometer EM-360A manufactured by Varian/Analytical Div. using TMS 
as an internal standard, and infrared absorption (IR) spectra were 
measured by means of a spectrophotometer of Model 281 manufactured by The 
Perkin-Elmer Corp. 
EXAMPLE I 
Preparation of Polyisothianaphthene by Treating 
1,3-Dihydroisothianaphthene-2-Oxide in Concd. Sulfuric Acid 
(a) Synthesis of 1,3-Dihydroisothianaphthene-2-Oxide 
To 200 ml of a solution containing 1 mol/l of lithium triethyl borohydride 
was added 3.21 g (0.1 mol) of powderous sulfur placed in a Schlenk flask 
at room temperature under a nitrogen atmosphere. The reaction immediately 
took place, and the sulfur powder was dissolved to form a yellow 
suspension. This suspension became a pale yellow clear solution upon 
contact with a trace amount of air. 
Separately, into a 2 liter-volume four-necked flask equipped with a 
dropping funnel, a stirrer, a thermometer and an inlet for introducing 
nitrogen were charged 26.4 g (0.1 mol) of o-xylylene dibromide and 1 liter 
of anhydrous tetrahydrofuran under a nitrogen atmosphere to form a 
solution. While stirring, the above prepared tetrahydrofuran solution of 
lithium sulfide was added thereto dropwise at room temperature over a 
period of 1.5 hours. Thereafter, the tetrahydrofuran was removed by 
distillation under reduced pressure and the residue was further distilled 
to obtain 10.9 g (yield: 80%) of colorless 1,3-dihydroisothianaphthene 
having a boiling point of 74.degree.-76.degree. C./3 mmHg. The IR spectrum 
of the product showed absorptions based on the phenyl group at 3060, 3026, 
1582 and 1485 cm.sup.-1 ; absorption based on the methylene group at 2910, 
2840 and 1450 cm.sup.-1 ; absorption based on in-plane deformation of 
1,2-substituted phenyl at 1195 cm.sup.-1 ; absorption of o-substituted 
phenyl at 760 cm.sup.-1 ; and absorption of sulfide at 740 cm.sup.-1. The 
results of NMR spectrum (.sup.1 H-NMR) measurement in CDCl.sub.3 with TMS 
as an internal standard are as follows: 4.22 (s, 4H); 7.20 (s, 4H). 
This compound was very labile and changed from yellow to black even when 
preserved under light-screening and sealing. 
Then, the thus obtained 1,3-dihydroisothianaphthene was added to 450 ml of 
a previously prepared 50% methanol aqueous solution having dissolved 
therein 18.6 g (0.086 mol) of sodium metaiodate, and the mixture was 
stirred at room temperature for 12 hours. The formed precipitate was 
separated by filtration. The filter cake was washed with 50 ml of 
methanol, and the washing and the filtrate were combined and concentrated 
under reduced pressure. The thus formed yellowish white solid was 
recrystallized from ethyl acetate-cyclohexane to obtain slightly 
yellow-tinged crystals having a melting point of 87.degree.-89.degree. C. 
The resulting crystals were further recrystallized from ethyl 
acetate-cyclohexane to obtain crystals having a melting point of 
90.degree. to 91.degree. C. The IR spectrum of the crystals showed strong 
absorption of sulfoxide at 1035 cm.sup.-1 in addition to the absorptions 
of isothianaphthene, and the absorption of sulfide at 740 cm.sup.-1 
disappeared. The 1H-NMR spectrum measured in CDCl.sub.3 with TMS as an 
internal standard were as follows: 4.65 (s, 4H); 7.20 (s, 4H). 
Elementary Analysis for C.sub.8 H.sub.8 SO: Calcd. (%): C 63.16; H 5.26; S 
21.05. 
Found (%): C 63.08; H 5.15; S 20.87. 
(b) Synthesis of Polyisothianaphthene from 
1,3-Dihydroisothianaphthene-2-Oxide (IIa, R.sup.1 =R.sup.2 =H) 
Five hundreds milligrams (3.29 mmol) of 1,3-dihydroisothianaphthene-2-oxide 
was added to 1 ml of concentrated sulfuric acid and the reaction system 
immediately turned dark red. The mixture was allowed to stand at room 
temperature for 70 hours, and the substantially solidified system was 
poured into 400 ml of methanol. The formed brown precipitate was separated 
by centrifugation, thoroughly washed with water and vacuum dried at 
60.degree. C. over night. The resulting polymer was placed in a Soxhlet's 
extractor and extracted successively with methylene chloride and 
chlorobenzene for 12 hours, respectively, to obtain 203 mg of a 
chlorobenzene insoluble matter. The IR spectrum of the resulting polymer 
were as shown in FIG. 1. The results of the elementary analysis were C: 
67.26%; H: 3.12%; and S: 23.59% and in fairly agreement with calculated 
values (C: 67.19%; H: 3.32%; S: 23.54%) on the assumption that the 
repeating unit had the following structure: 
##STR6## 
The electric conductivity (.delta..sub.RT) of the polymer at room 
temperature was measured by the use of a 4-terminal network conductivity 
measuring cell and was found to be 2.times.10.sup.-2 s/cm. 
EXAMPLE II 
Preparation of Polyisothianaphthene by Oxidation of 
Polydihydroisothianaphthene Obtained by Cationic Polymerization of 
Isothianaphthene with Oxidizing Agent 
(a) Synthesis of Isothianaphthene (IIb, R.sup.1 =R.sup.2 =H) 
Three hundreds milligrams (1.97 mmol) of 
1,3-dihydroisothianaphthene-2-oxide synthesized according to Example 1(a) 
and 450 mg (4.41 mmol) of neutral alumina were thoroughly pulverized and 
mixed in a mortar, then put in a sublimation apparatus and heated on an 
oil bath under reduced pressure. There was obtained 250 mg (1.87 mmol) of 
isothianaphthene as white needle crystals at the bottom of a cooling part 
of the sublimation apparatus. Immediately thereafter, the resulting 
monomer was dissolved in 5 ml of purified and degassed methylene chloride, 
and 10 mg of trifluoroacetic acid was added thereto, followed by allowing 
the mixture to stand overnight. When the reaction mixture was poured into 
50 ml of methanol, a white precipitate was obtained. The resulting polymer 
was soluble in chloroform, chlorobenzene, tetrahydrofuran and 
N,N-dimethylformamide. The IR and .sup.1 H-NMR spectra of the polymer were 
as shown in FIGS. 2 and 3, respectively. 
Further, it was confirmed that the polymer had a molecular weight of 2000 
as converted to polystyrene by gel-permeation chromatography (Varian 5000) 
of a tetrahydrofuran solution of the polymer. 
The electric conductivity (.delta..sub.RT) of the polymer at room 
temperature as measured in the same manner as in Example 1 was 10.sup.-8 
s/cm or less. 
Elementary Analysis for (C.sub.8 H.sub.6 S): 
Calcd. (%): C 71.64; H 4.48; S 23.88. 
Found (%): C 71.27; H 4.54; S 23.96. 
The same procedures as described above were repeated except for using 
methanesulfonic acid as a polymerization initiator in place of 
trifluoroacetic acid to obtain a polymer. The IR spectrum of the resulting 
polymer were in complete agreement with that of FIG. 2. 
These polymers were dissolved in 5 ml of chlorobenzene and treated with 
double the molar amount of chloranil to form a black precipitate. The 
resulting polymer had an electric conductivity (.delta..sub.RT) of 
9.times.10.sup.-2 s/cm at room temperature, and the electric conductivity 
of an iodine-doped polymer was 9.times.10.sup.-1 s/cm. IR spectrum of the 
polymer is shown in FIG. 4. The polymer after iodine-doping did not 
undergo change of conductivity even when left to stand in air at room 
temperature for 1 week. 
In the same manner as described above except for using 5 ml of chloroform 
in place of chlorobenzene and 1,1 times the molar amount of 
N-chlorosuccinimide in place of chloranil, a black polymer having entirely 
the same IR Spectrum as that shown in FIG. 4 was obtained. The 
conductivity (.delta..sub.RT) of this polymer was found to be 
2.6.times.10.sup.-1 s/cm. 
EXAMPLE III 
Preparation of Polyisothianaphthene by One-Step Oxidative Polymerization of 
Isothianaphthene 
Isothianaphthene was synthesized in the same manner as described in Example 
2(a). A mixture of 250 mg of isothianaphthene, 5 ml of anhydrous methylene 
chloride, 134 mg of anhydrous aluminum chloride and 134 mg of anhydrous 
cupric chloride was allowed to react at a temperature of 35 to 37.degree. 
C. for 1 hour to form a black precipitate. After the reaction mixture as 
such was maintained at that temperature for 12 hours, the precipitate was 
treated with a methanol solution having been rendered acidic with 
hydrochloric acid, thoroughly washed with water and dried. The dried 
polymer was extracted successively with hot methanol, hot methylene 
chloride and hot chlorobenzene to obtain 205 mg of a black polymer. The IR 
spectrum of this product was in complete agreement with FIG. 4. The 
electric conductivity (.delta..sub.RT) was 2.8.times.10.sup.-2 s/cm. 
EXAMPLE IV 
Preparation of Polyisothianaphthene by Electrochemical Polymerization of 
Isothianaphthene 
Electrochemical polymerization of isothianaphthene was carried out by using 
an electrolytic solution prepared by dissolving an electrolyte indicated 
in Table 1 below and isothianaphthene in a polar solvent at a prescribed 
concentration; a platinum plate as a sample electrode; an aluminum plate 
as a counter electrode; at room temperature at a constant voltage for a 
prescribed period of time. There was formed a polyisothianaphthene film on 
the platinum plate anode. The aforesaid electrolytic solution had been 
subjected in advance to disoxidation by bubbling dry argon gas 
therethrough for at least 30 minutes. The constant voltage during the 
polymerization was 1.5 V. 
The thus formed film was thoroughly washed successively with acetonitrile 
and methylene chloride and dried in vacuo. The electrical of the film 
properties were determined, and the results obtained are shown in Table 1 
below. 
TABLE 1 
__________________________________________________________________________ 
ELECTROCHEMICAL POLYMERIZATION 
OF ISOTHIANAPHTHENE 
Current 
Concentration of 
Electrolyte 
Solvent 
Application 
Property of Polymer 
Example 
Isothianaphthene 
(Concentration) 
(Amount) 
Time .sigma..sub.RT 
.sigma..sub.RT After 
Iodine-Doping 
No. (mmol/l) (mmol/l) (ml) (hr) Color 
(s/cm) (s/cm) 
__________________________________________________________________________ 
IV-1 78.8 .phi..sub.4 AsCl 
CH.sub.3 CN 
2 blackish 
4.5 .times. 10.sup.-2 
6.8 .times. 10.sup.-1 
(168) (25) blue 
IV-2 78.8 .phi..sub.4 PCl 
CH.sub.3 CN 
2 blackish 
-- -- 
(80) (25) blue 
IV-3 78.8 .phi..sub.4 AsCl 
.phi.CN 
2 blackish 
-- -- 
(168) (25) blue 
IV-4 78.8 Bu.sub.4 NBr 
.phi.CN 
2 blackish 
4 .times. 10.sup.-1 
-- 
(168) (25) blue 
IV-5 180 LiBr CH.sub.3 CN 
1 blackish 
-- -- 
(300) (25) blue 
IV-6 180 Bu.sub.4 NBr 
CH.sub.3 CN 
1 blackish 
4 .times. 10.sup.-1 
-- 
(300) (25) blue 
IV-7 180 Bu.sub.4 NPF.sub.6 
CH.sub.3 CN 
1 slightly 
-- -- 
(300) (25) purplish 
blue 
IV-8 180 Bu.sub.4 NClO.sub.4 
CH.sub.3 CN 
1 slightly 
-- -- 
(300) (25) purplish 
blue 
__________________________________________________________________________ 
Note: 
.phi..sub.4 AsCl: Tetraphenylarsonium chloride 
.phi..sub.4 PCl: Tetraphenylphosphonium chloride 
Bu.sub.4 NBr: Tetra(nbutyl)ammonium bromide 
LiBr: Lithium bromide 
Bu.sub.4 NPF.sub.6 : Tetra(nbutyl)ammonium hexafluorophosphate 
Bu.sub.4 NClO.sub.4 : Tetra(nbutyl)ammonium perchlorate 
CH.sub.3 CN: Acetonitrile 
.phi.CN: Benzonitrile 
EXAMPLE V 
Use of Polyisothianaphthene as Electrochemical Display Element, Battery 
Material, etc. 
Test of Use as Electrochromic Material 
The same procedures as in Example IV-2 were repeated but using a conductive 
glass on which indium oxide had been vacuum evaporated as an anode in 
place of platinum plate used in Example IV-2, thereby to electrochemically 
precipitate a polymer on the conductive glass. The cyclic voltammetry was 
performed using the above obtained polymer-coated conductive glass as a 
working electrode; a platinum wire as a counter electrode and a standard 
calomel electrode as a reference electrode; by the use of a polarographic 
analyzer (174A model manufactured by EG & G Co.) in an acetonitrile 
solution containing 292 mmol/1 of tetrabutylammonium perchlorate at room 
temperature. The applied voltage sweep rate was 20 mV/sec, and the range 
of sweep was from +1.0 V to -0.7 V (vs. standard calomel electrode). The 
results obtained are shown in FIG. 5. 
As is shown in FIG. 5, the polymer showed an oxidation peak and a reduction 
peak at +0.58 V and -0.15 V, respectively, and had a color varying from 
deep blue at a voltage range of from -0.7 V to +0.6 V to extremely 
transparent light green at a voltage range of from +0.6 V to +1.0 V. These 
results indicate that the deep blue state is a neutral state of the 
polymer and that the polymer has a green color of high transparency in the 
oxidized and doped state. 
Test of Use as Battery 
The polyisothianaphthene film obtained in Example IV-1 was cut into pieces 
of 1 cm wide and 3 cm long. One end of the sample piece was adhered to a 
platinum wire using a conductive adhesive, and this sample piece was 
arranged on each of both surfaces of a lithium foil of the same size via a 
1 mm thick porous polypropylene partitioning membrane in such a manner 
that an electrolytic solution could sufficiently impregnated thereinto. 
The system was then dipped in a propylene carbonate solution containing 
0.5 mol/l of lithium perchlorate to a depth of 2 cm. The thus prepared 
battery wherein the poly(isothianaphthene) was used as a cathode and the 
lithium foil as an anode was charged at a charging current of 2.0 
mA/cm.sup.2 for 30 minutes in an argon atmosphere. Completion of charging 
was immediately followed by discharging at a discharging current of 2.0 
mA/cm.sup.2, and at the time when the voltage of the battery fell to 1 V, 
charging was again performed under the same conditions as described above. 
When the charge-discharge operation was repeated in this manner, 590 times 
of repetition were recorded until the charge-discharge efficiency was 
reduced to 50%. Further, the charge-discharge efficiency on the 5th 
repetition was 99%. Furthermore, after 48-hour standing of a charged 
battery, the self discharging rate was 3.2%. 
EXAMPLE VI 
Poly(dihydroisothianaphthene) By Electrochemical Polymerization 
The monomer isothianaphthene was prepared by the procedure described in the 
literature (J. A. Gladysz et al., Tetrahedron, 1979, Vol. 35, 2239; M. P. 
Cava et al., J. Amer. Chem. Soc., 959, Vol. 81, 4266; M. P. Cava et al., 
J. Org. Chem., 1971, Vol. 36, 3932), and used directly after preparation. 
The polymer poly(dihydroisothianaphthene) was obtained by electrochemical 
oxidation of this monomer in a two-electrode, separate compartment cell. 
Platinum sheet was used as the anode, and oxidized graphite was used as 
the cathode. The clear colorless solution used for the polymerization 
contained 0.23 M of isothianaphthene with 0.30 M electrolyte, Bu.sub.4 
NPF.sub.6, in acetonitrile. The acetonitrile (Mallinckrodt) was used 
directly without further purification. A series of 1.5 V batteries was 
used as the power supply. 
All experiments were carried out under dry N.sub.2. When 4.5 V was 
connected across this cell, a lot of white powder appeared near the anode 
instantly. The batteries were disconnected after ten minutes. This white 
powder, poly(dihydroisothianaphthene), was separated by suction 
filtration, washed with acetonitrile and diethylether, and dried under 
vacuum. The resulting solid was purified for elemental analysis by 
reprecipitation from tetrahydrofuran-H.sub.2 O. 
When a freshly prepared sample of isothianaphthene was electrolyzed in the 
anode compartment of an H cell using Bu.sub.4 NClO.sub.4 or Bu.sub.4 
NBF.sub.4 as supporting electrolyte and tin oxide coated glass (TOG) as 
anode, a copious amount of a white precipitate ("WP") filled the anode 
compartment. Upon careful observation it was discovered that the anode was 
first (instantaneously) covered with a very thin blue film and immediately 
thereafter formation of WP commences. Appearance of WP was independent of 
electrode material, solvent, or temperature. Isolation, characterization 
(ir, el. anal.) and chemical manipulation (see below) proved WP to be 
poly(dihydroisothianaphthene). It should be noted that thiophene produces 
partially oxidized ("doped") polymer films under the above conditions 
while isothianaphthene, after deposition of an extremely thin blue film 
(presumably doped poly(isothianaphthene)), is transformed to 
poly(dihydroisothianaphthene). The only reasonable explanation for this 
surprising observation was that poly(isothianaphthene) acts as an 
initiator of cationic polymerization of isothianaphthene. In order to test 
this hypothesis we exposed freshly prepared solutions of isothianaphthene 
to the usual catalysts for cationic initiation (Bronsted and Lewis acids) 
and found that all polymerized isothianaphthene to different degrees. But 
by far the most interesting result was with sulfuric acid in methylene 
chloride. Under these conditions, isothianaphthene was converted to a 
blue-black powder form of poly(isothianaphthene) doped with hydrated 
sulfuric acid. Clearly the acid acted not only as catalyst but also as 
oxidizing agent. A reassuring "convergent" test for the above hypothesis 
was that the product of chloranyl dehydrogenation was 
poly(dihydroisothianaphthene) and the product of H.sub.2 SO.sub.4 
polymerization exhibited identical infrared spectra. The only reasonable 
explanation for this observation is that the infrared spectra of doped 
poly(isothianaphthene) are dominated by the absorptions due to the 
conduction electrons and the absorptions due to intramolecular vibrations 
are weak features of the spectrum. In the absence of additional control 
experiments, it is difficult to speculate about a specific mechanism to 
explain this electrolyte effect. 
We reasoned that H.sub.2 SO.sub.4 may convert 
dihydroisothianaphthene-S-oxide directly into poly(isothianaphthene). 
(H.sub.2 SO.sub.4).sub.x.(H.sub.2 O).sub.y. The addition of solid 
dihydroisothianaphthene-S-oxide to 98% H.sub.2 SO.sub.4 did in fact 
produce the desired partially doped poly(isothianaphthene) (cf Scheme I, 
below). 
##STR7## 
In addition, 7,7,8,8-tetracyanoquinodimethane can be used as a catalyst for 
cationic polymerization. However, the product did not exhibit higher 
conductivity than any of the other doped poly(isothianaphthene) compounds, 
indicating that the acceptor is probably not involved in the conductivity 
of the solid. Two reasons could be advanced for that observation, the 
acceptor molecules are probably not stacked in small crystalline regions 
and/or there is complete charge transfer. 
While the above results explain the nature of the process of formation of 
poly(dihydroisothianaphthene) and allow the discovery of a clean procedure 
for the chemical synthesis of poly(isothianaphthene), it still does not 
offer an entry to the electrochemical polymerization of isothianaphthene. 
This required the discovery of a method to prevent the catalysis for 
poly(dihydroisothianaphthene) formation by "nascent" doped 
poly(isothianaphthene). We found that if the reaction medium contained a 
species which was more nucleophilic than isothianaphthene, the propagation 
step would be interrupted. A test experiment which involved addition of 
iodide to the anode compartment prior to electrolysis failed because 
iodide was simply oxidized under the electrolysis conditions. However, 
electrolysis with LiBr, Bu.sub.4 NBr, or preferably Ph.sub.4 AsCl produced 
excellent films on platinum or TOG. The only reasonable explanation for 
this observation is that the infrared spectra of doped 
poly(isothianaphthene) are dominated by the absorptions due to the 
conduction electrons and the absorptions due to intramolecular vibrations 
are weak features of the spectrum. In the absence of additional control 
experiments, it is difficult to speculate about a specific mechanism to 
explain this electrolyte effect. 
Anal. Calcd. for (C.sub.8 H.sub.6 S): C, 71.60; H, 4.51; S, 23.89. Found: 
C, 71.27; H, 4.54; S, 23.96. 
LiBF.sub.4 and Bu.sub.4 NClO.sub.4 can be used as the electrolyte for this 
reaction. 
According to this invention, it has been found that the metastable 
isothianaphthene can be polymerized to well characterizable highly 
conducting polymers by at least three different procedures; one of these 
involves the electrochemical preparation of poly(dihydroisothianaphthene) 
by the polymerization of isothianaphthene in the presence of nucleophilic 
anions. It has also been found that poly(isothianaphthene) is a better 
conductor than polythiophene. 
EXAMPLE VII 
Poly(dihydroisothianaphthene) By Chemical Cationic Polymerization 
The monomer isothianaphthene (396 mg, 2.96 m.mol) was dissolved in 10 ml 
methylene chloride which was previously dried over P.sub.2 O.sub.5. When 
one drop of methanesulfonic acid was added to this solution, there was an 
instantaneous change in the reaction mixture from colorless to red. This 
color became violet after 90 minutes. After removal of methylene chloride 
by evaporation, the residue was dissolved in tetrahydrofuran. And when 
this solution was poured into methanol, the polymer 
poly(dihydroisothianaphthene) precipitated from the solution. This was 
separated by centrifugation, and dried under vacuum. The infrared spectrum 
was identical with that of polymer poly(dihydroisothianaphthene) mentioned 
above. 
The following Examples demonstrate the successful practice of the present 
invention and are not intended to be limiting of the invention. 
EXAMPLE VIII 
Doped Poly(isothianaphthene) By Electrochemical Polymerization 
The polymerization procedure was essentially the same as that described 
above in Example VI for the polymer poly(dihydroisothianaphthene). The 
most important point was the electrolyte. When lithium bromide was used as 
the electrolyte, a blue film of the doped polymer poly(isothianaphthene) 
was grown on the anode (conducting glass) instantly after connecting a 1.5 
V battery. Bu.sub.4 NBr and Ph.sub.4 AsCl can also be used as the 
electrolyte for this reaction. 
EXAMPLE IX 
Doped Poly(isothianaphthene) By Chemical Cationic Oxidative Polymerization 
With Sulfuric Acid 
Sulfuric acid (5 ml.) was added to the monomer isothianaphthene (396 mg. 
2.96 m.mol). The monomer color changed from white to reddish-black 
instantly. When the reaction mixture was poured into 400 ml of methanol 
after overnight stirring, a brown powder, the doped polymer 
poly(isothianaphthene) precipitated from this solution. This was separated 
by centrifugation and extracted with methylene chloride and chlorobenzene 
using a Soxhlet extraction apparatus, followed by drying under vacuum. 
This reaction can be also carried out with a suspension of sulfuric acid 
in methylene chloride. 
EXAMPLE X 
Doped Poly(isothianaphthene) By Chemical Cationic Oxidative Polymerization 
With TCNQ (7,7,8,8-Tetracyanoquinodimethane) 
The monomer isothianaphthene (238 mg. 1.77 m.mol) was dissolved in 5 ml 
methylene chloride. After a few mg of TCNQ were added to this solution, 
its color changed to red very slowly. After overnight stirring, this color 
became bluish-black. Next, more TCNQ which was double the molar quantity 
of the monomer isothianaphthene, was added to this solution. This was 
heated up to 110.degree. C. and this temperature was kept for 1 hour. When 
this reaction mixture was poured into methanol, greenish-black powder 
precipitated from this solution. This was washed with methanol and 
chloro-benzene using a Soxhlet extraction apparatus, followed by drying 
under vacuum. 
EXAMPLE XI 
Poly(isothianaphthene) From Poly(dihydroisothianaphthene) 
The polymer poly(dihydroisothianaphthene), which was prepared by 
electrochemical polymerization, was dissolved in hot chlorobenzene. This 
was a light-brown solution. Tetra-chloro-p-benzoquinone (Chloranyl) was 
added to this solution. Immediately the solution color changed to dark 
green. A powder precipitated from this solution by cooling. This was 
separated by suction filtration, washed with methanol, and dried under 
vacuum. All materials which were mentioned in Examples VII to XI showed 
identical infrared spectra. 
Thus, the present invention presents three alternative routes to 
poly(isothianaphthene): 
1. The electrochemical polymerization of isothianaphthene in the presence 
of nucleophilic anions; 
2. The chemical polymerization of isothianaphthene or 
dihydroisothianaphthene-S-oxide in the presence of cationic polymerization 
catalysts; 
3. The dehydrogenation of poly(dihydroisothianaphthene). 
Preliminary results of conductivity measurements are collected in Table II. 
The band edge of poly(isothianaphthene) was estimated (from transmission 
through thin films at low doping levels) to be .about.1 eV (1.1.mu.). This 
is nearly 1 eV lower than that of polythiophene (.about.2 eV, 620 
nm).sup.3. 
TABLE II 
______________________________________ 
List of Compaction Conductivity of the 
Doped Polymer Poly(isothianaphthene) 
Compound [S/cm].sup.a 
______________________________________ 
Poly(isothianaphthene).Cl.sub.x - Example VIII 
4.0 .times. 10.sup.-1 
Poly(isothianaphthene).(HSO.sub.4).sub.0.05.(H.sub.2 O).sub.0.033 
2.0 .times. 10.sup.-2 
Example Ib 
Poly(isothianaphthene).(AlCl.sub.4).sub.x - Example III 
2.8 .times. 10.sup.-2 
Poly(isothianaphthene).(TCNQ).sub.x - Example X 
1.5 .times. 10.sup.-2 
Poly(isothianaphthene).(Chloranyl).sub.4.sbsb.x - 
1.3 .times. 10.sup.-2 
Example XI 
______________________________________ 
.sup.a 2probe compaction measurement 
FIG. 9 shows the reversible electrochemical doping of 
poly(isothianaphthene). Thus, using aluminum as one electrode (with a 
standard calomel reference electrode), the poly-(isothianaphthene) as the 
other electrode, and a propylene carbonate solution of lithium 
fluoroborate as the electrolyte, it can be seen that the polymers of this 
invention are useful as battery electrodes. 
The experiment of FIG. 9 also demonstrates the electrochromic 
characteristics of the novel polymers of this invention. 
In FIG. 6, we show the electrochromic effect; the dopant was 
ClO.sub.4.sup.-. The reference electrode was lithium. The Energy (eV) 
refers to the incident radiation, with the 0 to 1 range being in the 
infrared, 1 to 2 the visible, and 2 and above gradually shifting to the 
ultraviolet portion of the spectrum. The results shown in FIG. 6 
furthermore indicate the utility of the polymers of this invention in 
solar energy conversion devices because the semiconductor energy gap is 
well matched to the solor spectrum. 
The present inventors have conducted extensive investigations on 
electrochromic behaviors of a polymer having an isothianaphthene structure 
and, as a result, found that the above-described polymer is a novel 
electrochromic material which is rapid in response and provides a 
substantially colorless tone in an oxidized state, and thus accomplished 
the present invention. This finding is admittedly surprising because such 
an electrochromic material that assumes a substantially colorless tone is 
not hitherto known. 
The electrochromic display device (ECD) according to the present invention 
comprises a conductive transparent base having provided thereon a high 
molecular weight conductive membrane and an opposing electrode arranged 
thereunder via a liquid electrolyte and is characterized in that said high 
molecular weight conductive membrane is a polymer having an 
isothianaphtlene structure and capable of being reversibly oxidized or 
reduced. The term "liquid electrolyte" herein used means a dispersion or 
solution of a supporting electrolyte in a solvent. 
Specific Explanation of the Invention 
The high molecular weight conductive membrane which can be used as an 
electrochromic layer according to the present invention is a polymer 
capable of being reversibly oxidized or reduced and having an 
isothianaphthene structure represented by the formula (III): 
##STR8## 
wherein R.sup.1 and R.sup.2 represent hydrogen or hydrocarbon having a 
carbon number of 1-5, X is sulfur, selenium or tellurium, Y.sup.- 
represents an anion, z is a value of 0-0.40 representing the ratio of 
anion per isothianaphthene structure unit, and n represents the degree of 
polymerization of 5-500, which is produced by electrochemically 
polymerizing isothianaphtene compound expressed by the following formula 
(IV): 
##STR9## 
wherein R.sup.1, R.sup.2 and X are as defined immediately above. 
Specific examples of the isothianaphthene compound represented by the 
formula (IV) include 1,3-isothianaphthene, 5-methyl-1,3-isothianaphthene, 
5,6-dimethylisothianaphthene, 5-ethyl-1,3-isothianaphthene, 
5-methyl-6-ethyl-1,3-isothianaphthene, etc. 
Electrochemical polymerization of the above-described isothianaphthene 
compound can be carried out according to the methods generally employed 
for electrochemical polymerization of thiophene, pyrrole, etc. [e.g., the 
method described in Solid State Communication, Vol. 46, No. 5, 389 
(1983)]. More specifically, both controlled potential electrolysis or 
controlled current electrolysis can be employed, and it is desirable to 
form a polymer membrane on a transparent base by using a conductive 
transparent base as a sample electrode. 
The conductive transparent base which can be used in the present invention 
include the ones comprising a transparent insulator such as glass, 
polyester film, etc. having vacuum evaporated thereon indium-tin oxide, 
tin oxide, platinum, etc. by sputtering or a like method, which are easily 
available as commercial products. The polymer membrane formed by 
electrochemical polymerization has a thickness of from 0.03 to 30 .mu.m, 
preferably 0.05 to 22 .mu.m, more preferably 0.1 to 10 .mu.m. The membrane 
thickness can be controlled by the quantity of electricity applied in the 
electrochemical polymerization. When the membrane thickness is less than 
0.03 .mu.m, clear contrast cannot be attained, leading to substantial loss 
of commercial value as a display material. To the contrary, a thickness 
exceeding 30 .mu.m provides clear contrast but is unfavorable in view of 
film strength or response speed. 
ECD devices can be produced by assembling the thus obtained polymer with an 
opposing electrode via a liquid electrolyte. The liquid electrolyte which 
can be used is a dispersion or solution of a supporting electrolyte in a 
solvent. The supporting electrolyte which can be used in the present 
invention includes combinations of (i) anions (i.e., Y.sup.- in the 
formula (III)) such as halide anions of Va group elements, e.g., 
PF.sub.6.sup.-, SbF.sub.6.sup.-, AsF.sub.6.sup.- and SbCl.sub.6.sup.- ; 
halide anions of IIIa Group series element, e.g., BF.sub.4.sup.- ; halogen 
anions, e.g., I.sup.- (I.sub.3.sup.-), Br.sup.- and Cl.sup.- ; perchloric 
acid anions, e.g., ClO.sub.4.sup.- ; and (ii) cations such as alkali metal 
ions, e.g., Li.sup.+, Na.sup.+ and K.sup.+ ; quaternary ammonium ions, 
e.g., R.sub.4 N.sup.+ (wherein R represents a hydrocarbon residue having 1 
to 20 carbon atoms); and phosphonium ions, e.g., (C.sub.6 H.sub.5).sub.4 
P.sup.+, but these combinations are not limitative. 
Specific examples of the supporting electrolytes composed of the 
above-described combinations of anions (X) and cations are LiPF.sub.6, 
LiSbF.sub.6, LiAsF.sub.6, LiClO.sub.4, NaI, NaPF.sub.6, NaSbF.sub.6, 
NaAsF.sub.6, NaClO.sub.4, KI, KPF.sub.6, KSbF.sub.6, KAsF.sub.6, 
KClO.sub.4, [(n-Bu).sub.4 N].sup.+.(AsF.sub.6).sup.-, [(n-Bu).sub.4 
N].sup.+. (PF.sub.6).sup.-, [(n-Bu).sub.4 N].sup.+.ClO.sub.4.sup.-, 
LiAlCl.sub.4, LiBF.sub.4, (C.sub.6 H.sub.5).sub.4 P.BF.sub.4, (C.sub.6 
H.sub.5).sub.4 P.AsF.sub.6 and (C.sub.6 H.sub.5).sub.4 P.ClO.sub.4, but 
these examples are not limitative. These supporting electrolytes may be 
used individually or in combination of two or more of them if necessary. 
HF.sub.2.sup.- anion can also be used in addition to the above-enumerated 
anions. Further, cations which can be used in addition to the 
above-enumerated ones include pyrylium or pyridinium cations represented 
by the following formula (V) and carbonium cations represented by the 
following formula (VI) or (VII): 
##STR10## 
wherein Z represents an oxygen atom or a nitrogen atom; R' represents a 
hydrogen atom, an alkyl group having 1 to 15 carbon atoms or an aryl group 
having 6 to 15 carbon atoms; R" represents a halogen atom, an alkyl group 
having 1 to 10 carbon atoms or an aryl group having 6 to 15 carbon atoms; 
m is 0 when Z is an oxygen atom, or m is 1 when Z is a nitrogen atom; and 
p is 0 or an integer of from 1 to 5. 
##STR11## 
wherein R.sup.3, R.sup.4 and R.sup.5 each represents a hydrogen atom, an 
alkyl group having 1 to 15 carbon atoms, an allyl group, an aryl group 
having 6 to 15 carbon atoms or -OR.sup.7 wherein R.sup.7 represents an 
alkyl group having 1 to 10 carbon atoms or an aryl group having 6 to 15 
carbon atoms, with proviso that R.sup.3, R.sup.4 and R.sup.5 are not 
hydrogen atoms at the same time; and R.sup.6 represents a hydrogen atom, 
an alkyl group having 1 to 15 carbon atoms or an aryl group having 6 to 15 
carbon atoms. 
The HF.sub.2.sup.- anion which can be used is usually obtained by 
dissolving a compound (hydrofluoride) represented by the formula (VIII), 
(IX) or (X): 
EQU R'.sub.4 N.HF.sub.2 (VIII) 
EQU M.HF.sup.2 (IX) 
##STR12## 
wherein R' and R" each represents a hydrogen atom, an alkyl group having 1 
to 15 carbon atoms or an aryl group having 6 to 15 carbon atoms; R'" 
represents an alkyl group having 1 to 10 carbon atoms or an aryl group 
having 6 to 15 carbon atoms; Z represents an oxygen atom or a nitrogcn 
atom; q represents 0 or a positive integer of 5 or less; and M represents 
an alkali metal, as a supporting electrolyte in an appropriate solvent. 
Specific examples of the compounds represented by the above formulae 
(VIII), (IX) and (X) include H.sub.4 N.HF.sub.2, Bu.sub.4 N.HF.sub.2, 
Na.HF.sub.2, K.HF.sub.2, Li.HF.sub.2 and 
##STR13## 
The pyrylium or pyridinium cations represented by the formula (III) can be 
obtained by dissolving a salt formed between a cation represented by the 
formula (V) and an anion (X), e.g., ClO.sub.4.sup.-, BF.sub.4.sup.-, 
AlCl.sub.4.sup.-, FeCl.sub.4.sup.-, SnCl.sub.5.sup.-, PF.sub.6.sup.-, 
PCl.sub.6.sup.-, SbF.sub.6.sup.-, AsF.sub.6.sup.-, CF.sub.3 
SO.sub.3.sup.-, HF.sub.2.sup.-, etc., as a supporting electrolyte in an 
appropriate solvent. Specific examples of such a salt are: 
##STR14## 
Specific examples of the carbonium cations represented by the 
above-described formula (VI) or (VII) include (C.sub.6 H.sub.5).sub.3 
C.sup.+, (CH.sub.3).sub.3 C.sup.+, 
##STR15## 
etc. 
These carbonium cations can be obtained by dissolving or dispersing a salt 
formed between such a cation and an anion (X) (i.e., carbonium salt) as a 
supporting electrolyte in an appropriate solvent. The anion (X) usable 
typically includes BF.sub.4.sup.-, AlCl.sub.4.sup.-, AlBr.sub.3 Cl.sup.-, 
FeCl.sub.4.sup.-, PF.sub.6.sup.-, PCl.sub.6.sup.-, SbCl.sub.6.sup.-, 
SbF.sub.6.sup.-, ClO.sub.4.sup.-, CF.sub.3 SO.sub.3.sup.-, etc., and the 
carbonium salt specifically includes, for example, (C.sub.6 H.sub.5).sub.3 
C.BF.sub.4, (CH.sub.3).sub.3 C.BF.sub.4, HCO.AlCl.sub.4, HCO.BF.sub.4, 
C.sub.6 H.sub.5 CO.SnCl.sub.5, etc. 
The solvents which can be used in the present invention may be either an 
aqueous solvent or a non-aqueous solvent, but a solution of the aforesaid 
supporting electrolyte in a non-aqueous organic solvent is preferred. 
Preferably, the organic solvents herein used are aprotic and have high 
dielectric constants. For example, ethers, ketones, nitriles, amines, 
amides, sulfur compounds, phosphoric ester compounds, phosphorous ester 
compounds, boric ester compounds, chlorinated hydrocarbons, esters, 
carbonates, nitro compounds and the like can be employed. Of these, 
ethers, ketones, nitriles, phosphoric ester compounds, phosphorous ester 
compounds, boric ester compounds, chlorinated hydrocarbons and carbonates 
are preferred. Specific examples of these solvents include 
tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, monoglyme, 
acetonitrile, propionitrile, 4-methyl-2-pentanone, butyronitrile, 
valeronitrile, benzonitrile, 1,2-dichloroethane, .gamma.-butyrolactone, 
valerolactone, dimethoxyethane, methylformate, propylene carbonate, 
ethylene carbonate, dimethylformamide, dimethyl sulfoxide, dimethyl 
thioformamide, ethyl phosphate, methyl phosphate, ethyl phospite, methyl 
phosphite, 3-methylsulforan, etc. Among these, nitriles and carbonates are 
especially preferred in order to increase the response speed. 
These organic solvents may be used alone or in combination of two or more 
of them. 
Depending upon the model of ECD devices used or the kind of electrodes 
used, oxygen or water present in these solvents or protonic solvents 
sometimes deteriorate performances of the ECD devices. Such being the 
case, it is preferable to previously purify the solvents in a usual 
manner. Further, in the ECD devices of the present invention, organic 
solvents having merely dispersed therein a supporting electrolyte, or an 
organic solid electrolyte having high ionic conductivity which is composed 
of polyethylene oxide and NaI, NaSCN, etc. can also be used in addition to 
the above-described electrolytes. 
Concentrations of the supporting electrolyte used in the ECD devices of 
this invention vary depending on the kind of organic solvents used, 
current and voltage values of applied electricity, operating temperatures, 
the kind of supporting electrolytes and the like and, therefore, cannot be 
generally fixed. The liquid electrolyte may be either homogeneous or 
heterogeneous, but usually employable concentrations range from 0.001 to 
10 mol/l. The distance between the high molecular weight conductive 
membrane and an opposing electrode cannot be generally determined since it 
varies depending on the kind of supporting electrolytes, current and 
voltage values of applied electricity, the display surface area as an ECD 
device and the like, but it is preferably from 0.05 to 5 mm. Further, as 
an opposing electrode, a variety of materials can be employed according to 
the end use. That is, in the case when transmitted light is utilized for 
displaying, the conductive transparent materials as described above are 
preferably used as opposing electrodes. On the other hand, in the case of 
utilizing reflected light, it is also possible to use, as opposing 
electrodes, opaque conductive materials, such as a metal foil, e.g., 
nickel or platinum, and gauze. Furthermore, since the ECD devices provide 
a substantially colorless tone, background plates having various color 
tones can be selected. Thus, the ECD devices obtained by the present 
invention can be used in a wide application owing to a wide selection of 
materials to be used. 
The present invention will now be illustrated in greater detail with 
reference to examples, but it should be understood that the present 
invention is not limited to these examples. 
EXAMPLE XII 
In an acetonitrile solution containing 0.08 mol/l of (C.sub.6 
H.sub.5).sub.4 PCl was dissolved 0.0788 mol/l of 1,3-isothianaphthene (the 
compound of the formula (IV) wherein R.sup.1 =R.sup.2 =H) to prepare an 
electrolyte. Electrochemical polymerization was carried out by using the 
above electrolyte, a glass plate on which indium tin oxide had been vacuum 
evaporated as a sample electrode, an aluminum plate as a counter electrode 
at a current density of 2 mA/cm.sup.2 at room temperature for 20 minutes. 
There was obtained an electrochemically lightly doped, deep blue-colored 
polymer on the indium tin oxide-deposited glass plate anode. The resulting 
display base was washed with acetonitrile and dried. The dry thickness of 
the polymer membrane was 10 .mu.m. 
The thus produced display base was immersed in a tetrahydrofuran solution 
containing 0.53 mol/l of LiClO.sub.4, and electricity was imposed 
therethrough using Li as a counterelectrode to determine dependence on 
applied voltage. The results obtained are shown in FIG. 6. As can be seen 
from FIG. 6, the polymer had a blue color at 2.50 V (vs. Li electrode) but 
turned to transparent pale green at 3.50 V. It was also confirmed that 
this change was reversible. 
Then, voltammetry was performed using (C.sub.4 H.sub.9).sub.4. NClO.sub.4 
as an electrolyte in acetonitrile at an applied voltage of from -0.7 V to 
+1.0 V (vs. a standard calomel electrode). The results obtained are shown 
in FIG. 7. It can be seen from FIG. 7 that the polymer film had a deep 
blue color at a voltage of from +0.6 V to -0.7 V and changed to a highly 
transparent pale green color at a voltage of from +0.6 to +1.0 V. 
According to these results, an ECD device as shown in FIG. 8 was produced, 
and a propylene carbonate solution containing 0.53 mol/l of LiBF.sub.4 was 
incorporated therein as a liquid electrolyte and then sealed. Square waves 
of +0.8 V to -0.4 V were applied to the ECD device at a frequency of 1 Hz 
to effect a durability test. As a result, no deterioration of the 
electrochromic material was observed even after 2.times.10.sup.4 times of 
coloring and discoloring operations. 
Having fully described tho invention, it is intended that it is to be 
limited only by the lawful scope of the appended claims.