Electrochromic composition

Abstract

The present invention relates to an electrochromic composition comprising at least one reducing compound and at least two oxidizing compounds, said at least two oxidizing compounds having similar oxydo-reduction potentials. More specifically, said at least two oxidizing compounds are selected from viologen derivatives. Said composition can be used as a variable transmittance medium for the manufacture of an optical article, such as an ophthalmic lens.

Claims

1. An electrochromic composition comprising: at least one reducing compound; and at least two electrochromic oxidizing compounds, wherein said electrochromic oxidizing compounds have similar oxydo-reduction potentials, and are selected from viologen derivatives of formulae (I) and (II): ##STR00100## wherein: R.sup.1 and R.sup.2 are each independently selected from optionally substituted phenyl groups; R.sup.3, R.sup.4, R.sup.5 and R.sup.6 are each independently selected from H, alkyl, alkoxy, alkylthio, haloalkyl, haloalkoxy, haloalkythio, polyakylenoxy, alkoxycarbonyl, aryl, substituted aryl, heteroaryl and substituted heteroaryl, wherein the alkyl group may be substituted by one or more substituents independently selected from alkoxy, cycloalkyl, aryl, substituted aryl, heteroaryl and substituted heteroaryl; n, p, q and r are each independently an integer from 0 to 4, wherein when n, p, q or r is two or more, each of the R.sup.3, each of the R.sup.4, each of the R.sup.5 or each of the R.sup.6 may be identical or different; A and B are respectively selected from nitrogen and —N.sup.+(R.sup.7a)—, and from nitrogen and —N.sup.+(R.sup.7b)—, wherein R.sup.7a and R.sup.7b are independently selected from: alkyl which may be substituted by one or more groups independently selected from halogen, alkoxy, cycloalkyl, vinyl, allyl, aryl, substituted aryl, heteroaryl and substituted heteroaryl; aryl and heteroaryl which may be both substituted by one or more groups independently selected from: halogen, cyano, nitro, alkyl, haloalkyl, arylalkyl, cycloalkyl, cycloalkylalkyl and heterocycloalkylalkyl, alkenyl, alkynyl, allyl, vinyl, aryl, substituted aryl, heteroaryl, substituted heteroaryl, —N(aryl).sub.2, —N(aryl)CO(aryl), —CO-aryl and —CO-substituted aryl; —OR.sup.8, —S(O)R.sup.8, —S(O.sub.2)R.sup.8, —S(O.sub.2)NR.sup.8R.sup.9, —NR.sup.8R.sup.9, —NR.sup.8COR.sup.9, —NR.sup.8CO(aryl), —NR.sup.8aryl, —CH.sub.2OR.sup.8, —CH.sub.2SR.sup.8, —CH.sub.2R.sup.8, —CO—R.sup.8 and —CO.sub.2R.sup.8 wherein R.sup.8 and R.sup.9 are independently selected from H, alkyl, haloalkyl, arylalkyl, cycloalkyl, cycloalkylalkyl and heterocycloalkylalkyl; —S(O.sub.2)NR.sup.10R.sup.11 and —NR.sup.10R.sup.11, wherein R.sup.10 and R.sup.11 form together with the nitrogen atom to which they are linked a saturated 5 to 7 membered heterocycloalkyl which may comprise in addition to the nitrogen atom one further heteroatom selected from oxygen, nitrogen and sulphur, and which may be optionally substituted by one or two groups independently selected from halogen, —R.sup.8, —OR.sup.8, and —NR.sup.8R.sup.9, wherein R.sup.8 and R.sup.9 are as defined above; —V—W—R.sup.12 wherein: V is selected from oxygen, —N(R.sup.8)—, sulphur, —S(O)— and —S(O.sub.2)— wherein R.sup.8 is as defined above; W is alkylene, which may be substituted by one or more groups independently selected from halogen and alkoxy; and R.sup.12 is selected from —OR.sup.8, —NR.sup.8(alkyl) and —SR.sup.8 wherein R.sup.8 is as defined above; and —OC(O)—R.sup.13 wherein R.sup.13 is selected from alkyl, haloalkyl, alkenyl, —W—R.sup.12, and aryl group which may be substituted by 1 to 4 groups selected from halogen, —R.sup.8, —OR.sup.8, —SR.sup.8, —NR.sup.8R.sup.9, —NR.sup.10R.sup.11, —CO—R.sup.8, C(O)OR.sup.8, wherein R.sup.8, R.sup.9, R.sup.10, R.sup.11, R.sup.12 and W are as defined above; Z is selected from: alkylene; cycloalkylene; and a bivalent groups of formula —R.sup.14—Y—R.sup.15—, wherein: R.sup.14 and R.sup.15 are each independently selected from single bond, alkylene and cycloalkylene, and Y is selected from arylene, cycloalkylene, heteroarylene, arylene-arylene or arylene-CR′R″-arylene wherein R′ and R″ form together with the carbon to which they are linked a carbocyclic group; wherein said alkylene, cycloalkylene, arylene, heteroarylene and carbocyclic groups may be substituted by one or more substituents selected from halogen, alkyl, alkoxy, alkylthio, hydroxyalkyl, acyloxy, cycloalkyl, aryl, substituted aryl, aryloxy heteroaryl and substituted heteroaryl; m is 2 if A and B are nitrogen, 3 if one of A and B is nitrogen and the other is not nitrogen, and 4 if both A and B are not nitrogen; X.sup.− is a counterion; at least one of the viologen derivatives is selected from compounds of formula (I); and at least one of the viologen derivative is selected from compounds of formula (III) or formula (IV): ##STR00101## wherein Z, and X.sup.− are as defined in formula (II), and R.sup.16 and R.sup.17 are independently selected from substituted phenyl groups of formula (VI): ##STR00102## wherein R.sub.a and R.sub.b are independently selected from H, halogen, cyano, nitro, hydroxyl, alkyl, haloalkyl, alkoxy, haloalkoxy, alkylthio, acyl, aroyl, alkoxycarbonyl, cycloalkyl, allyl, aryl, benzyl, and heteroaryl provided that at least one of R.sub.a and R.sub.b is not H ##STR00103## wherein R.sup.4, R.sup.5, Z, A, B, m and X.sup.− are as defined in formula (II) and at least one of R.sup.4 and R.sup.5 is not H.

2. The electrochromic composition according to claim 1, wherein the oxydo-reduction potentials of the electrochromic oxidizing compounds differ from each other from less than 0.2 V.

3. The electrochromic composition according to claim 2, wherein the oxydo-reduction potentials of the electrochromic oxidizing compounds differ from each other from less than 0.15 V.

4. The electrochromic composition according to claim 3, wherein the oxydo-reduction potentials of the electrochromic oxidizing compounds differ from each other from less than 0.1 V.

5. The electrochromic composition according to claim 4, wherein the oxydo-reduction potentials of the electrochromic oxidizing compounds differ from each other from less than 0.05 V.

6. The electrochromic composition according to claim 1, wherein Z is selected from C.sub.1-C.sub.12 alkylene, aryl substituted C.sub.1-C.sub.12 alkylene, phenylene, naphthylene, (C.sub.1-C.sub.4 alkylene)-phenylene-(C.sub.1-C.sub.4 alkylene), (C.sub.1-C.sub.4 alkylene)-naphthylene-(C.sub.1-C.sub.4 alkylene), quinoxaline-2,3-diyl, (C.sub.1-C.sub.4 alkylene)-quinoxaline-2,3-diyl-(C.sub.1-C.sub.4 alkylene), phenylene-phenylene, (C.sub.1-C.sub.4 alkylene)-phenylene-phenylene-(C.sub.1-C.sub.4 alkylene) and phenylene-fluorenylene-phenylene.

7. The electrochromic composition according to claim 6, wherein Z is selected from —CH.sub.2—, —(CH.sub.2).sub.2—, —(CH.sub.2).sub.3—, —(CH.sub.2).sub.4—, —(CH.sub.2).sub.5—, —CH.sub.2—CH(CH.sub.3)—CH.sub.2—, —CH.sub.2—CH(CH.sub.2Phenyl)-CH.sub.2—, —(CH.sub.2).sub.2—CH(CH.sub.3)—CH.sub.2—, —(CH.sub.2).sub.3—CH(CH.sub.3)—CH.sub.2—, —(CH.sub.2).sub.2—CH(CH.sub.3)—(CH.sub.2).sub.2—, ##STR00104## ##STR00105##

8. The electrochromic composition according to claim 1, wherein R.sup.3, R.sup.4, R.sup.5 and R.sup.6 are each independently selected from C.sub.1-C.sub.4 alkyl, C.sub.1-C.sub.4 alkoxycarbonyl, alkanoyl, aroyl, aryl and heteroaryl, and wherein the aryl and heteroaryl may be substituted by one or more substituents selected from C.sub.1-C.sub.4 alkyl and C.sub.1-C.sub.4 haloalkyl.

9. The electrochromic composition according to claim 1, wherein the counterion X.sup.− is selected from halide, tetrafluoroborate, tetraphenylborate, hexafluorophosphate, nitrate, methanesulfonate, trifluoromethane sulfonate, toluene sulfonate, hexachloroantimonate, bis(trifluoromethanesulfonyl)imide, perchlorate, acetate and sulfate.

10. The electrochromic composition according to claim 1, wherein said viologen derivatives are selected from compounds I-1 to I-50, III-7 to III-19 and IV-1 and IV-14: TABLE-US-00008 Compound Formula I-1 I-2 I-3 I-4 I-5 I-6 I-7 I-8 I-9 I-10 I-11 I-12 I-13 I-14 I-15 I-16 I-17 I-18 I-19 I-20 I-21 I-22 I-23 I-24 I-25 I-26 I-27 I-28 I-29 I-30 I-31 I-32 I-33 I-34 I-35 I-36 I-37 I-38 I-39 I-40 I-41 I-42 I-43 I-44 I-45 I-46 I-47 I-48 I-49 I-50 III-7 III-8 III-9 III-10 III-11 III-12 III-13 III-14 III-15 III-16 III-17 III-18 III-19 IV-1 IV-2 IV-3 IV-4 IV-5 IV-6 IV-7 IV-8 IV-9 IV-10 IV-11 IV-12 IV-13 IV-14 wherein Me represents methyl, Ph represents phenyl and Tol represents 4-methylphenyl.

11. The electrochromic composition according to claim 1, wherein the reducing compound is selected from: ferrocene and their derivatives; phenoxazine and their derivatives; phenazine and their derivatives; phenothiazine and their derivatives; thioanthrene; and tetrathiafulvalene.

12. The electrochromic composition according to claim 11, wherein said composition comprises a fluid, mesomorphous or gel host medium.

13. An electrochromic device comprising the electrochromic composition as defined in claim 1.

14. The electrochromic device according to claim 13, wherein said electrochromic device comprises a mechanism for holding the composition in a mechanically stable environment.

15. The electrochromic device according to claim 13, wherein said electrochromic device comprises at least one transparent electrochromic cell comprising a pair of opposed substrates facing each other and forming a gap, and the gap is filled with the electrochromic composition.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) FIG. 1—cell assembly and filling procedure.

EXAMPLES

(2) This invention will be further illustrated by the following non-limiting examples which are given for illustrative purposes only and should not restrict the scope of the appended claims.

Evaluation of Oxido-Reduction Potential and Colour of the Compounds Used for the Preparation of the Electrochromic Composition:

(3) The oxido-reduction potentials of the compounds were measured by a method of cyclic voltammetry with 3 electrodes.

(4) The 3 electrodes used were: 1 Platinum working electrode 1 Platinum auxiliary or counter electrode 1 Platinum reference electrode which is immersed into a solution consisting of 0.01M AgNO.sub.3+0.1M TBAP (tetrabutylamonium perchlorate) in acetonitrile.

(5) The potential values indicated were the first reduction potential for the compounds, with regards to the standard hydrogen reference electrode (SHE).

(6) The analyzed solution comprised 0.01M of the compound to be analyzed and 1M of TBAP salt.

(7) The scan rate of the potential was fixed to 100 mV/s.

(8) The colour of the analyzed compounds was evaluated with a solution comprising 0.01M of the compound to be analyzed, 0.02M Phenothiazine (Phtz) or 10-Methylphenothiazine (Mephtz) and 1M of TBAP salt in propylene carbonate as solvent.

(9) This solution was introduced into a quartz tank where at least one glass electrode coated with Indium Tin Oxide (ITO) is placed in order to colour the analyzed compound on this electrode.

(10) The reducing agent (phenothiazine for all compounds except compounds, III-3, III-10 and III-11 using 10-methylphenothiazine) coloured on another glass electrode coated with Indium Tin Oxide (ITO).

(11) The potential applied between both electrodes, for activating the compounds, was equal to the addition, in absolute value, of E.sup.1.sub.red of the compound+E.sup.1.sub.ox of phenothiazine (which is E.sup.1.sub.ox=0.36V) or methylphenothiazine (which is E.sup.1.sub.ox=0.45V).

(12) The results for each of the synthesized compounds are indicated in Table 1 below. E1red corresponds to the first reduction potential.

(13) The colours indicated in Table 1 to 6 is the visual colour perceived by emmetropic eyes under day light conditions.

(14) TABLE-US-00002 TABLE 1 Com- E.sup.1.sub.red pound Molecule (V) Colour I-5  −0.69 green I-10  −0.7  green III-10 −0.64 purple III-11 −0.58 purple

(15) 1—Preparation of the Electrochromic Compositions:

Example 1

(16) Combination of I-10 (1,1′-bis(3-(tert-butyl)phenyl)-[4,4′-bipyridinel]-1,1′-diium)bis tetrafluoroborate+III-10 (1′,1′″-(Propane-1,3-diyl)bis{1-(2-(trifluoromethoxy)phenyl)-[4,4′-bipyridinel]-1,1′-diium} tetrakis(tetrafluoroborate))+MePhtz

(17) The compounds I-10, III-10 and methyphenothiazine were dissolved in a solution comprising propylene carbonate, the PMMA and the tetrabutylammonium tetrafluoroborate. At the end of this preparation step, a limpid and non or weakly visible light absorbing solution was obtained.

(18) Table 2 indicates the amount of each compound of the electrochromic composition of Example 1, the oxydo-reduction potential of reducing compound and oxidizing compounds as well as their colour state when they are activated individually.

(19) E.sub.1red corresponds to the first reduction potential and E.sub.1ox to the first oxidation potential. The oxydo-reduction potentials of I-10 and III-10 differ from each other from about 0.06 Volt.

(20) TABLE-US-00003 TABLE 2 Compound Solvent Propylene Thickening agent Carbonate PMMA Electrolyte (PC) (Mw = 97.000 g/mol) I-10 III-10 MePhtz TBA BF.sub.4.sup.− Molar 0.08M 0.014M 0.13M 0.13M concentration Weight 82.1% 7.8% 3.5% 1.1% 2.2% 3.3% percent Potential E.sub.1red max E.sub.1red max E.sub.1ox max (Volt) −0.70 −0.64 0.44 Colour at the green purple red activated state

(21) The non-activated state of the composition of Example 1 was uncoloured. After activation at a potential of between 0.9 and 1.1 V, the activated state obtained was brown.

(22) The change of state was totally reversible.

Example 2

Combination of I-5 (1,1′-bis(4-(tert-butyl)phenyl)-[4,4′-bipyridinel]-1,1′-diium)bis tetrafluoroborate+III-10 (1′,1′″-(Propane-1,3-diyl)bis{1-(2-(trifluoromethoxy)phenyl)-[4,4′-bipyridine]-1,1′-diium}tetrakis(tetrafluoroborate))+MePhtz

(23) Same preparation as in example 1 except that the compound I-10 was replaced by I-5.

(24) Table 3 indicates the amount of each compound of the electrochromic composition of Example 2, the oxydo-reduction potential of reducing compound and oxidizing compounds as well as their colour state when they are activated individually.

(25) TABLE-US-00004 TABLE 3 Compound Thickening agent Solvent PMMA Electrolyte PC (Mw = 97.000 g/mol) I-5 III-10 MePhtz TBA BF.sub.4.sup.− Molar 0.08M 0.014M 0.13M 0.13M concentration Weight 82.1% 7.8% 3.5% 1.1% 2.2% 3.3% percent Potential E.sub.1redmax E.sub.1redmax E.sub.1oxmax (Volt) −0.69 −0.64 0.44 Colour at the green purple red activated state

(26) The non-activated state of the composition of Example 2 was uncoloured. After activation at a potential of between 0.9 and 1.1 V, the activated state obtained was brown. The change of state was totally reversible.

Example 3

Combination of I-10 (1,1′-bis(3-(tert-butyl)phenyl)-[4,4′-bipyridinel]-1,1′-diium)bis tetrafluoroborate+III-1 (1,1′″-(Propane-1,3-diyl)bis{1-(4-(trifluoromethoxy)phenyl)-[4,4′-bipyridinel]-1,1′-diium}tetrakis(tetrafluoroborate))+MePhtz

(27) Same preparation as example 1 except that the compound III-10 was replaced by III-11. Table 4 indicates the amount of each compound of the electrochromic composition of Example 3, the oxydo-reduction potential of reducing compound and oxidizing compounds as well as their colour state when they are activated individually.

(28) TABLE-US-00005 TABLE 4 Compound Thickening agent Solvent PMMA Electrolyte PC (Mw = 97.000 g/mol) I-10 III-11 MePhtz TBA BF.sub.4.sup.− Molar 0.08M 0.014M 0.13M 0.13M concentration Weight 82.1% 7.8% 3.5% 1.1% 2.2% 3.3% percent Potential E.sub.1redmax E.sub.1redmax E.sub.1oxmax (Volt) −0.69 t −0.58 0.44 Colour at the green purple red activated state

(29) The non-activated state of the composition of Example 3 was uncoloured. After activation at a potential of between 0.9 and 1.1 V, the activated state obtained was brown. The change of state was totally reversible.

Example 4

Combination of I-10 (1,1′-bis(3-(tert-butyl)phenyl)-[4,4′-bipyridinel]-1,1′-diium)bis tetrafluoroborate+III-10 (1′,1′″-(Propane-1,3-diyl)bis{1-(2-(trifluoromethoxy)phenyl)-[4,4′-bipyridinel]-1,1′-diium}tetrakis(tetrafluoroborate))+ferrocene:

(30) Same preparation as example 2 except that the reducing compound methyphenothiazine was replaced partially by ferrocene.

(31) Table 5 indicates the amount of each compound of the electrochromic composition of Example 4, the oxydo-reduction potential of reducing compound and oxidizing compounds as well as their coloured state when they are activated individually.

(32) TABLE-US-00006 TABLE 5 Compound Thickening agent Solvent PMMA Electrolyte PC (Mw = 35000 g/mol) I-10 III-10 Ferrocene MePhtz TBA BF4− Molar 0.12M 0.028M 0.08M 0.19M 0.2M concentration Weight 67.4% 16.9% 5% 2% 1.1% 2.8% 4.8% percent Potential E.sub.1redmax E.sub.1redmax E.sub.1oxmax E.sub.1oxmax (Volt) −0.70 −0.64 0.12 0.44 Colour at the green purple uncoloured activated state

(33) The non-activated state of the composition of Example 4 was uncoloured. After activation at a potential at 0.64 V, the activated state obtained was grey. The change of state was totally reversible.

(34) 2—Implementation of the Electrochromic Composition in an Electrochromic Device

(35) The cell used to evaluate the electrochromic compositions included two mineral glass substrates facing each other. The internal sides of these substrates were coated with transparent conductive electrodes. The transparent conductive material used here was indium tin oxide (ITO). The substrates were held at fixed distance from one another by using spacers of 75 μm, in order to form a gap. The edge of the cell was sealed with a UV curable adhesive in such a way that an opening of 5 mm is left.

(36) A tank was filled at room temperature and atmospheric pressure with the electrochromic composition of the present invention. The cell was placed vertically in the tank under atmospheric pressure in such way that the opening was located above the solution level. The tank with the cell was placed in a vacuum-desiccator, which was evacuated to 0.5mBar. The opening of the cell was then introduced in the solution. During the aeration of the tank under the introduction of an inert gas, for example Ar or N.sub.2, the electrochromic composition filled the entire volume of the gap through the opening. The opening was then sealed with a UV curable adhesive in order to make the cell hermetic. The electrical connection is made by two silver plated copper wires, sealed on each ITO glass substrates with silver charged epoxy adhesive.

(37) The electrical potential applied to test the electrochromic cell was monitored by a potentiostat.

(38) The cell assembly and filling procedure used are illustrated in FIG. 1.

(39) 3—Evaluation of the Compositions (Colour, Transmittance, Stability . . . ) with Detailed Methods

(40) A series of experiments was performed on the composition obtained in Examples 1-4.

(41) Transmission

(42) The transmission spectra of the solution incorporating the composition of the invention was measured.

(43) The transmission level or visual transmittance (Tv) of the lens was also measured according to the ISO Standard 8980-3, in the 380 nm-780 nm wavelength range, using a spectrophotometer. It corresponds to the transmission factor as defined in the ISO Standard 13666:1998.

(44) The optical performance was assessed by means of transmission measurements. A lens is regarded as “low visible light absorbing” if its Tv is higher than 70%, preferably higher than 80%.

(45) It is to be noted that the cell used for the purpose of the experiment is a basic device, and that its Tv value at the empty state, i.e. before filing with the electrochromic formulation, is only 70%. Said Tv value could be simply increased by using classical methods, for example by adding anti-reflective coating, etc. . . .

(46) Colour

(47) The electrochromic cell as described above was filled with the composition of Examples 1 to 4.

(48) When a potential was applied between the electrodes of the electrochromic device, the solution/composition which was initially colourless, changes rapidly to a brown colour. The solution returned rapidly to its colourless state when the potential was removed. The potential applied for activating the solution is indicated in Table 6.

(49) Stability/Ageing Performance

(50) In order to study the stability of the formulation, the solutions/compositions of examples 1 to 4 were activated under an application of a potential during 40 hours. After 40 hours of application, switching off the voltage caused the colour rapidly to disappear for the examples 1 to 4.

(51) The results of these properties for each composition are summarized in table 6.

(52) TABLE-US-00007 TABLE 6 Visual Colour Visual Stability/ Transmittance in the Transmittance ageing in bleached Potential activated in activated perfomance state (Tv) (Volt) state state (Tv) (40 hours) Example 1 78% 1.0 brown 9% Ok Example 2 75% 1.0 brown 2% Ok Example 3 74% 1.0 brown 3% Ok Example 4 75% 0.64 brown 9.5%.sup.  Ok

(53) As can be seen from the data of Table 6, the compositions of examples 1 to 4 according to the invention in their inactive or bleached state exhibited a good transmittance in the 410-800 nm wavelength range, between 70% and 80%. When a potential was applied between the electrodes of the electrochromic device, the compositions of examples 1 to 4 according to the invention which were all initially colourless or of weakly visible light absorbing changed rapidly to a brown colour. The compositions then returned rapidly to their colourless state when the potential is removed.

(54) The compositions of examples 1 to 4 also exhibited good stability. Indeed after 40 hours of application of a voltage, once the voltage was switched off, all the compositions of examples 1 to 4 returned rapidly to their initial clear state.