Electrochromic solution

Abstract

The present invention relates to an electrochromic solution and its use, wherein the solution comprises: a solvent; a thickening polymer agent having a molecular weight of at least 50,000 g / mol, preferably 200,000 g / mol, more preferably at least 250,000 g / mol; at least one additive having a molecular weight between 300 and 50,000 g / mol, preferably between 320 and 20,000 g / mol; a redox chemical mixture in dissolved state in the solvent, the mixture consisting of at least one electrochromic reducing compound and at least one electrochromic oxidizing compound, and coloring in the presence of an applied voltage and bleaching to a colorless state in the absence of an applied voltage. The present invention further relates to a device comprising the solution.

Description

[0001] This invention relates to a novel electrochromic solution comprising a thickening polymer having a molecular weight of at least 50,000 g / mol and at least one additive, and to the use of such a solution as a variable transmittance medium in the manufacture of optical articles such as optical lenses, optical filters, attenuators, windows, visors, goggles, mirrors, and displays.

[0002] Electrochromism is a well-known physical phenomenon where certain types of compounds reversibly change color when a voltage is applied, and this physical phenomenon is observed. Materials undergo reversible changes in optical properties through oxidation and reduction. These redox reactions of the compounds provide the device with a "self-erasing" characteristic. Typically, electrochromic materials are colorless when no electric field is applied and can be colored when an electric field is applied. Electrochromic devices, i.e., devices containing electrochromic compounds, have absorbance that depends only on the presence of an electric field, and therefore can have two states: a colored state (when electroactivated) and a faded state (inactive state). The optical transmission properties of the device depend on the electrochromic compound.

[0003] Electrochromic systems can be applied to a variety of applications. For example, in ophthalmology, electrochromic lenses allow users to actively control the darkening of the lens under certain lighting conditions to provide eye protection, and quickly switch when these conditions change. This contrasts with photochromic lenses, which passively darken under UV radiation and require some time to fade again when UV radiation stops. Furthermore, photochromic dyes are typically incorporated into ophthalmic lenses via an infiltration (or impregnation) method unsuitable for any ophthalmic substrate. Electrochromic glasses are also used in the manufacture of "smart windows" or rearview mirrors. Generally, all these electrochromic devices are made from electrochromic compositions that contain a solvent in addition to the electrochromic compound. This is called an electrochromic solution.

[0004] In the case of electrochromic self-erasing solutions, there are two issues that need to be controlled: color segregation and current leakage.

[0005] Color segregation issues arise from prolonged continuous operation of electrochromic systems. When the initial fading occurs after extended operation or coloring by removing electrical energy, the fading within the device is typically uneven. This problem is visually perceived as segregated color bands that slowly dissipate near the transparent electrical elements present within the electrochromic system. Therefore, segregation is due to the migration and convection of the coloring material remaining near these electrical elements. From an aesthetic, commercial, and functional perspective, the presence of such color bands is unacceptable because it impairs the clarity of the visual information collected by the user from a device containing an electrochromic system.

[0006] The difference in solubility between the colored and uncolored forms of any colored substance can also cause segregation. This form of segregation is particularly evident in electrochromic devices where the principal plane is not horizontal during use, such as those encountered in automotive rearview mirrors, wall mirrors, architectural windows, front, rear, and side windows of automobiles, optical lenses, eyeglasses, etc. In their colored forms, any one or two of the colored substances can completely or partially separate from the electrochromic solution depending on their solubility, and may float or sink depending on their density relative to the bulk solvent.

[0007] Another problem encountered in electrochromic self-erasing devices involves current leakage. When the electrochromic unit colors the solution by applying a voltage, the coloring substances of the redox pairs continuously tend to recombine and return to their equilibrium, which is a colorless state. The recombination rate of the coloring substances in the bulk solution is related to their diffusion coefficient in the solvent used. To compensate for the tendency of the coloring substances to recombine and enter the colorless equilibrium state, current must continuously leak into the electrochromic solution through conductive electrodes typically sandwiched between the solution.

[0008] Since current must flow through the conductive surface of the transparent electrical element used on at least one of the substrates sandwiching the electrochromic unit, and since these transparent electrical elements have finite sheet resistance, the applied potential will be highest near the connector, which is typically located around the edge of the unit, and lowest near the center of the device when current passes through the conductive glass surface to color the remote area.

[0009] Therefore, if the leakage current is high, the potential drop generated on the transparent conductor itself results in a lower potential being applied to the distant regions. This leads to uneven coloring. The edge regions closest to the electrical components are the darkest, while the central regions are the lightest. This coloring gradient is unacceptable, and therefore it is necessary to ensure that the dark coloring is uniform throughout the solution.

[0010] Furthermore, leakage current needs to be as low as possible to minimize current consumption. Low current consumption is crucial because the battery powering the electrochromic system in the device is small. In the case of ophthalmic lenses, the battery must be as small as possible for both aesthetic and ergonomic reasons.

[0011] However, low leakage current affects the fading rate. The fading rate is the time it takes for an electrochromic device to return from a fully or partially colored state to a substantially transparent, uncolored state. Reducing the leakage current would simultaneously slow down the fading rate, which is commercially unacceptable.

[0012] To achieve the commercially desirable device described above, a balance needs to be struck between color depth, color uniformity, and a relatively rapid fading rate.

[0013] While adding only a thickener such as polymethyl methacrylate (PMMA) might be effective because it increases the viscosity of the electrochromic solution and helps reduce segregation, such agents are known to be disadvantageous because they reduce current leakage and simultaneously decrease the fading rate. One problem with adding only a thickener is that the solution can become so viscous that methods for manufacturing electrochromic devices become industrially impractical.

[0014] Reference US 5145609 describes electrochromic solutions containing polyether polymers in propylene carbonate solvent. It was found that adding linear polyether polymers such as polyethylene oxide (PEO) instead of polymethyl methacrylate (PMMA) eliminated the segregation effect with a limited reduction in leakage current and therefore a limited fading rate. However, none of these polymers showed satisfactory solubility in propylene carbonate solvent. While low molecular weight PEO is insoluble in propylene carbonate, PMMA can be soluble, but dissolution at room temperature takes a long time, making both unattractive.

[0015] Document US 5142407 describes an electrochromic solution containing cyanoethyl sucrose in propylene carbonate solvent. By replacing polymethyl methacrylate with cyanoethyl sucrose, which has higher solubility in propylene carbonate, color uniformity is improved, segregation is reduced, and leakage current is reduced to a limited extent. However, the viscosity of the electrochromic solution obtained according to this document is typically less than 100 centistokes (cSt) when measured at 25°C, which is too low to completely eliminate the segregation effect. Furthermore, cyanoethyl sucrose is a yellow liquid, making it unsuitable for the production of transparent products.

[0016] Therefore, there is a need to obtain improved electrochromic solutions for use as transparent and homogeneous media for forming high-quality articles, especially high-quality ophthalmic lenses, wherein the solutions exhibit low segregation effects on the one hand, and relatively high fading rates and low leakage currents obtained by low recombination of coloring substances within the solution bulk on the other hand, and wherein these solutions are sufficiently viscous, preferably exhibiting a viscosity of less than 3000 cP at 25°C, so that the obtained solutions are suitable for the production of electrochromic devices.

[0017] Following extensive research, according to a first aspect, the inventors of this invention provide an electrochromic solution comprising:

[0018] - Solvent;

[0019] - A thickening polymer agent having a molecular weight of at least 50,000 g / mol, preferably at least 200,000 g / mol, and more preferably at least 250,000 g / mol;

[0020] - At least one additive having a molecular weight between 300 and 50,000 g / mol, preferably between 320 and 20,000 g / mol; preferably, the additive is in a liquid state;

[0021] - A redox chemical mixture in a dissolved state in the solvent, the mixture comprising at least one electrochromic reducing compound and at least one electrochromic oxidizing compound, and colored in the presence of an applied voltage and fading to a colorless state in the absence of an applied voltage.

[0022] In electrochromic solutions, the use of this thickener together with at least one other additive helps to reduce segregation while maintaining a viscosity of less than 3000 cP at 25°C.

[0023] While using high molecular weight compounds (i.e., thickening polymers) helps avoid phase separation problems, using low molecular weight compounds (i.e., additives) helps control current consumption.

[0024] The solvent used in the electrochromic solution according to the invention is an inert solvent selected from, but not limited to, ethylene carbonate, propylene carbonate, γ-butyrolactone, γ-valerolactone, acetonitrile, propionitrile, benzyl nitrile, glutaronitrile, methylglutaronitrile, dimethylformamide, N-methylpyrrolidone, sulfolane, 3-methylsulfolane, methyl propionate, ethylene glycol, ethylene carbonate, propylene glycol diacetate, propylene glycol methyl ether acetate, ionic liquids, and mixtures thereof. Preferably, the solvent is propylene carbonate.

[0025] More specifically, this invention relates to an electrochromic solution wherein the thickening polymer is electrochemically inert and soluble in the solvent used. The thickening polymer used in this invention has a molecular weight of at least 50,000 g / mol, preferably at least 200,000 g / mol, more preferably at least 250,000 g / mol and at most 1,000,000 g / mol, preferably at most 800,000 g / mol, more preferably at most 650,000 g / mol.

[0026] Preferably, the thickening polymer is a vinyl acetate polymer having a molecular weight of at least 50,000 g / mol, preferably at least 200,000 g / mol, more preferably at least 250,000 g / mol, preferably at least 300,000 g / mol, more preferably at least 350,000 g / mol, even more preferably at least 400,000 g / mol and at most 1,000,000 g / mol, preferably at most 800,000 g / mol, more preferably at most 650,000 g / mol.

[0027] More preferably, the solvent is propylene carbonate, and the thickening polymer is a vinyl acetate polymer having a molecular weight of at least 200,000 g / mol, preferably at least 250,000 g / mol.

[0028] A preferred example of a thickening polymer that can be used in this invention is a vinyl acetate polymer (PVAC or polyvinyl acetate) sold by Wacker under the name Vinnapas UW25FS, having a molecular weight of 540,000 g / mol as measured by size exclusion chromatography (SEC).

[0029] The electrochromic solution further contains additives selected from ester derivatives of benzoic acid or ester derivatives of phthalic acid, or mixtures thereof.

[0030] Similar to thickening polymers, additives must also be soluble in the solvent used and electrochemically inert, preferably having an electrochemical window higher than 2V.

[0031] The molecular weight of the additive is between 300 and 50,000 g / mol. Preferably, its molecular weight is higher than 400 g / mol. It has been observed that additives with a molecular weight higher than 300 g / mol are effective in reducing leakage current.

[0032] Preferably, its molecular weight is less than 20,000 g / mol, less than 18,000 g / mol, even more preferably less than 15,000 g / mol or even less than 10,000 g / mol.

[0033] The additive can be in liquid or solid form. Preferably, the additive is in liquid form.

[0034] According to the embodiments, the additive is selected from ester derivatives of benzoic acid having formula (I) or (II).

[0035]

[0036] R1 and R2 may be similar or different and are selected from H, optionally substituted alkyl groups (such as optionally substituted arylalkyl groups), optionally substituted aryl groups, and optionally substituted cycloalkyl groups.

[0037] The group (or radical) defined above may be replaced by one or more substituents, such as halogen, alkyl, alkoxy, aryl, heteroaryl, haloalkyl, haloalkoxy, alkoxycarbonyl, alkylacyl, arylacyl, formyl, nitrile, nitro, amide, alkylthio, alkylsulfinyl, alkylsulfonyl, arylthio, arylsulfinyl, arylsulfonyl, amino, alkylamino, arylamino, dialkylamino, and diarylamino.

[0038] The term "alkyl" refers to any monovalent group comprising a straight-chain or branched hydrocarbon chain containing 1 to 18 carbon atoms. Examples of C1-C18 alkyl groups include C1-C4 alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, or tert-butyl; C6-C8 alkyl groups such as n-hexyl, n-heptyl, or n-octyl; and n-pentyl, 2-ethylhexyl, 3,5,5-trimethylhexyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, or n-octadecyl.

[0039] The term "cycloalkyl" refers to any monovalent group in a monocyclic or bicyclic 3- to 12-membered saturated carbon ring. Examples of C3-C12 cycloalkyl groups include cyclopropyl, cyclopentyl, and cyclohexyl.

[0040] The term "aryl" refers to any monovalent group in an aromatic hydrocarbon containing 6 to 18 carbon atoms. Examples of C6-C18 aryl groups include phenyl, naphthyl, anthraceneyl, and phenanthrene.

[0041] The expression "arylalkyl" means, for example, benzyl or phenyl (C2-C7 alkyl).

[0042] Preferably, R 1 Both R and R2 are hydrogen atoms.

[0043] In the above formula (I), n is an integer ranging from 1 to 10, preferably from 1 to 7, and more preferably from 1 to 4.

[0044] In the above formula (II), m is an integer ranging from 1 to 10, preferably from 1 to 7, and more preferably from 1 to 4.

[0045] In this embodiment, the additive is preferably selected from a list of ester derivatives of benzoic acid, comprising polypropylene glycol dibenzoate (PPGDB) such as dipropylene glycol dibenzoate (DPGDB) and tripropylene glycol dibenzoate (TPGDB), polyethylene glycol dibenzoate (PEGDB) such as diethylene glycol dibenzoate (DEGDB) and triethylene glycol dibenzoate (TEGDB), and mixtures thereof.

[0046] The dipropylene glycol dibenzoate (DPGDB) that can be used advantageously is, for example, the dipropylene glycol dibenzoate sold by COIM under the name Plaxter B271.

[0047] Polyethylene glycol dibenzoate (PEGDB) that can be used advantageously is, for example, PEGDB sold by Sigma-Aldrich, which has a molecular weight of 410 g / mol and a boiling point of 217 °C. Compounds containing both glycol and aromatic units are particularly advantageous. The glycol unit helps to increase the solubility of the additive in the solvent used, and the presence of the aromatic unit helps to increase the boiling point.

[0048] Alternatively, the additive may be selected from a list of ester derivatives of phthalic acid, consisting of bis(2-ethylhexyl phthalate) (DEHP), diisononyl phthalate (DINP), di-n-octyl phthalate (DNOP), diisodecyl phthalate (DIDP), dipropylheptyl phthalate (DPHP), di-2-ethylhexyl terephthalate (DOTP or DEHT), and mixtures thereof.

[0049] In another embodiment, the additive may be selected from a list of glycol derivatives, such as polyethylene glycol diacrylate (or methacrylate), polyethylene glycol diepoxide, polypropylene glycol diacrylate (or methacrylate), polypropylene glycol diepoxide, and mixtures thereof, provided that the molecular weight of the additive is between 300 and 50,000 g / mol.

[0050] Alternatively, the additive may be selected from a list of low molecular weight polymers (<50,000), such as poly(methyl methacrylate) (PMMA), polyvinyl acetate (PVA, PVAc, PVAC or poly(vinyl acetate)), polyvinyl butyral (PVB), cellulose acetate butyrate (CAB) and mixtures thereof, provided that the molecular weight of the additive is between 300 and 50,000 g / mol.

[0051] According to an embodiment, the electrochromic solution may contain at least two additives independently selected from one of the ester derivatives of benzoic acid, one of the ester derivatives of phthalic acid, one of the glycol derivatives, or one of the low molecular weight polymers, such as a mixture of a benzoic acid derivative and a glycol derivative, a mixture of at least two ester derivatives, or a mixture of at least two glycol derivatives, provided that the at least two additives are well miscible.

[0052] The additive content is from 5 to 60 wt% by weight relative to the total weight of the electrochromic solution, preferably from 10 to 30 wt%, and more preferably from 15 to 25 wt%.

[0053] The content of the thickening polymer is from 1 to 30 wt% by weight, preferably from 3 to 20 wt%, and more preferably from 5 to 15 wt% relative to the total weight of the electrochromic solution.

[0054] The viscosity of the electrochromic solution is no greater than 3000 cP at 25°C, preferably no greater than 2500 cP at 25°C, and even more preferably less than 2000 cP at 25°C. Excessively high viscosity is undesirable because it leads to a longer filling process of the electrochromic solution in the final device, which is undesirable from an industrial point of view.

[0055] Therefore, it is preferable to keep the solid content (i.e., thickening polymer, additives, electrochromic compound) of the electrochromic solution as low as possible, preferably less than 45 wt% relative to the total weight of the solution, and even more preferably less than 30 wt% relative to the total weight of the solution.

[0056] In a preferred embodiment, the electrochromic solution is a liquid. For the same reasons mentioned above, liquid additives are preferred.

[0057] Another factor affecting the length of the filling process is the melting point of the electrochromic solution. To avoid a long filling process, the melting point of the solution needs to be kept below -20°C.

[0058] According to a preferred embodiment, the thickening polymer is a vinyl acetate polymer present in 5 to 15 wt% by weight relative to the total weight of the electrochromic solution, and the additive is a polypropylene glycol dibenzoate or polyethylene glycol dibenzoate present in 15 to 25 wt% by weight relative to the total weight of the electrochromic solution.

[0059] The at least one reducing compound in the solution of the present invention is not particularly limited. The at least one reducing compound is not necessarily an electrochromic compound; however, it should be selected from compounds having at least the following properties: low absorption of visible light in the bleached state (if the reducing compound is also an electrochromic compound), good stability, especially against oxygen, and good solubility in conventional electrochromic solvents such as propylene carbonate.

[0060] Preferably, at least one electrochromic reducing compound is selected from ferrocene and its derivatives such as ethylferrocene and tert-butylferrocene, phenoxazine and its derivatives such as N-benzylphenoxazine, phenazine and its derivatives such as 5,10-dihydrophenazine and N,N,N',N'-tetramethyl-p-phenylenediamine, phenothiazine and its derivatives such as 10-methylphenothiazine and isopropylphenothiazine; thioanthraene; and tetrathiofulvalene. Preferably, the electrochromic reducing compound is 10-methylphenothiazine.

[0061] The at least one electrochromic oxidizing compound in the solution of the present invention is not particularly limited. The at least one electrochromic oxidizing compound is selected from monovioletin or bisvioletin (i.e., 4,4'-bipyridinium salt or bis[4,4'-bipyridinium] salt), such as alkylvioletin, arylvioletin, arylalkylvioletin, alkylarylvioletin, or anthraquinone and its derivatives.

[0062] Non-limiting examples of such viologen compounds or viologen derivatives, more specifically examples of substituted dialkyl, diaryl 4,4'-bipyridinium salts, substituted dialkyl, diaryl bis[4,4'-bipyridinium] salts and mixtures thereof, are described in references EP 2848667 A1, EP 2848668 A1, EP 2848669 A1, EP 2848670 A1, EP 3115433 A1 and EP3345981 A1, the teachings of which are incorporated herein by reference. Preferred examples are mentioned herein.

[0063] At least one electrochromic oxidizing compound may be ethyl viologen diperchlorate.

[0064] In a preferred embodiment, the electrochromic solution comprises at least one reducing compound, preferably one reducing compound (such as 10-methylphenothiazine) and at least one electrochromic oxidizing compound, preferably at least two electrochromic oxidizing compounds, such as two or three electrochromic oxidizing compounds, preferably each electrochromic oxidizing compound is independently selected from substituted dialkyl 4,4'-bipyridinium salts, substituted diaryl 4,4'-bipyridinium salts, substituted dialkyl bis[4,4'-bipyridinium] salts or substituted diaryl bis[4,4'-bipyridinium] salts, more preferably the at least two electrochromic oxidizing compounds are at least one substituted diaryl 4,4'-bipyridinium and at least one substituted diaryl bis[4,4'-bipyridinium].

[0065] Preferably, at least one oxidizing compound is selected from or at least two electrochromic oxidizing compounds are independently selected from a series of compounds.

[0066]

[0067]

[0068]

[0069]

[0070]

[0071]

[0072]

[0073]

[0074]

[0075]

[0076]

[0077] More preferably, at least one electrochromic oxidizing compound is selected from or at least two electrochromic compounds are selected from the series of compounds below.

[0078]

[0079]

[0080]

[0081]

[0082]

[0083]

[0084]

[0085] In a particularly preferred embodiment, the redox chemical mixture comprises the following:

[0086] - A reducing compound, and

[0087] - At least one electrochromic oxidizing compound, preferably at least two electrochromic oxidizing compounds

[0088] The at least one electrochromic oxidizing compound is a compound having formula Ia or a compound having formula IIa, and the at least two electrochromic oxidizing compounds are selected from the group consisting of compounds having formula Ia and compounds having formula IIa.

[0089]

[0090] Compounds having formula Ia

[0091] Where R 3 and R 4 Selected independently from:

[0092] as well as

[0093] And X -It is a counterion selected from halide ions, tetrafluoroborate, tetraphenylborate, hexafluorophosphate, nitrate, methanesulfonate, trifluoromethanesulfonate, toluenesulfonate, hexachloroantimonate, bis(trifluoromethanesulfonyl)imide, perchlorate, acetate, and sulfate.

[0094]

[0095] Compounds having formula (IIa)

[0096] Where Z is -CH2-, -(CH2)2-, -(CH2)3-, -(CH2)4-, -(CH2)5-, -CH2-CH(CH3)-CH2-, -CH2-CH(CH2phenyl)-CH2-, -(CH2)2-CH(CH3)-CH2-, -(CH2)3-CH(CH3)-CH2-, -(CH2)2-, and CH(CH3)-(CH2)2-.

[0097] And R 5 and R 6 The phenyl group is selected from alkyl groups and optionally substituted phenyl groups, preferably substituted phenyl groups, which are independently selected from:

[0098] as well as

[0099] According to a preferred embodiment, the redox chemical mixture is selected from a mixture of 10-methylphenothiazine and at least two electrochromic oxidizing compounds, wherein the at least two electrochromic oxidizing compounds are selected from the group consisting of compounds having formulas I-10 and II-10 and I-38 and II-10.

[0100]

[0101]

[0102] The compositions of the present invention may further comprise an inert current-carrying electrolyte. The inert current-carrying electrolyte should be compatible with the other components of the composition. In particular, the inert current-carrying electrolyte should not react with electrochromic compounds.

[0103] Examples of inert current-carrying electrolytes include, but are not limited to, alkali metal salts, lithium, sodium or tetraalkylammonium salts, aluminum chloride and aluminum boride, persulfates and bis(fluorosulfonyl)imides. The inert current-carrying electrolyte is preferably selected from sodium, lithium and tetraalkylammonium ions in combination with an inert anion, preferably selected from chloride ions, tetrafluoroborate, hexafluoroborate and perchlorate ions.

[0104] Other examples of inert anions include tetraphenylborate, cyano-triphenylborate, tetramethoxyborate, tetrapropoxyborate, tetraphenoxyborate, perchlorate, chloride, nitrate, sulfate, phosphate, methanesulfonate, ethanesulfonate, tetradecanesulfonate, pentadecanesulfonate, trifluoromethanesulfonate, perfluorobutanesulfonate, perfluorooctanesulfonate, benzenesulfonate, chlorobenzenesulfonate, toluenesulfonate, butylbenzenesulfonate, tert-butylbenzenesulfonate, dodecylbenzenesulfonate, trifluoromethylbenzenesulfonate, hexafluorophosphate, hexafluoroarsenate, or hexafluorosilicate. The most preferred inert current carrier electrolyte is tetra-n-butyltetrafluoroborate ammonium.

[0105] When present in an electrochromic composition, the concentration of the inert current-carrying electrolyte is typically from 0.005 to 2 M, preferably from 0.01 to 1 M, and more preferably from 0.05 to 0.5 M.

[0106] Suitable additional additives for electrochromic media used for occasional desired protection against UV light (<350nm) are, for example, UV absorbers. An example is 2,4-dihydroxybenzophenone (…). 3000, BASF, 2-hydroxy-4-n-octyloxybenzophenone ( 3035, Clariant, 2-(2H-benzotriazol-2-yl)-6-dodecyl-4-methylphenol ( 571, Ciba Specialty Chemicals, Inc., 2,2'-Dihydroxy-4-methoxy-benzophenone (Cyasorb 24) TM American Cyanamid Company, ethyl 2-cyano-3,3-diphenylacrylate ( 3035, BASF), 2-cyano-3,3-diphenyl-acrylate 2-ethylhexyl ester ( 3039, BASF), 2-ethylhexyl p-methoxycinnamate ( 3088, BASF), 2-hydroxy-4-methoxy-benzophenone ( 90, Ciba Specialty Chemicals), dimethyl 4-methoxybenzyl methylene malonate ( PR-25 (Clariant Corporation).

[0107] Additional additives used in electrochromic solutions may be selected from durable dyes or heat stabilizers.

[0108] Preferably, all components of the composition, except for the electrochromic compound, are substantially transparent to visible light, such that when the electrochromic compound is in its faded state, the composition appears substantially transparent to visible light or exhibits the color of a durable dye (if present).

[0109] According to a second aspect, the present invention relates to an electrochromic device comprising an electrochromic solution as defined in the first aspect.

[0110] Electrochromic devices include mechanisms for maintaining a solution in a mechanically stable environment.

[0111] The electrochromic device includes at least one transparent electrochromic unit, which includes a pair of opposing substrates facing each other and forming a gap, and the gap is filled with an electrochromic solution as defined herein.

[0112] More generally, all the characteristics described above for the electrochromic solution also apply to the electrochromic device, which is another object of the present invention. Conversely, all the characteristics described below for the device also apply to the electrochromic solution.

[0113] Preferably, the electrochromic solution has a neutral color in the colored state.

[0114] The electrochromic device is selected from optical articles, such as optical lenses or optical filters or attenuators, windows, sun visors, goggles, mirrors and displays, preferably optical lenses, such as ophthalmic lenses, more preferably ophthalmic lenses and goggles.

[0115] Non-limiting examples of ophthalmic lenses include corrective and uncorrective lenses, including single-vision or multi-vision lenses (i.e., afocal, single-vision, bifocal, trifocal, and progressive lenses), which may be segmented or non-segmented, and other elements for correcting, protecting, or enhancing vision, including but not limited to contact lenses, intraocular lenses, magnifying lenses (such as contrast-enhancing lenses for augmented reality or virtual reality devices), and protective lenses (such as sunglasses or sunglass lenses) or visors. Non-limiting examples of display elements and devices include screens and monitors. Non-limiting examples of windows include automotive, marine, and aircraft windows, filters, attenuators, shaders, and optical switches.

[0116] The device may contain functional layers, such as polarizing layers, photochromic layers, antireflective coatings, visible and UV absorbing coatings, impact-resistant coatings, abrasion-resistant coatings, anti-fog coatings, anti-fogging coatings, and dust-proof coatings, all of which are familiar to those skilled in the art. The electrochromic device of the present invention may include mechanisms for maintaining the composition in a mechanically stable environment. For example, the electrochromic device of the present invention includes an electrochromic unit comprising two substrates facing each other. The substrates are preferably optical substrates, such as any inorganic or organic glass commonly known and used in the field of optics. For example, it may be a sodium-calcium or borosilicate inorganic glass. It may be a thermoplastic resin, such as thermoplastic polycarbonate (PC), PET, PEN, PMMA, COC, COP, PVDC, cellulose triacetate, or a thermosetting or photocurable resin, such as polyurethane, polyurethane / polyurea (such as...). The substrate used to manufacture the electrochromic device can be spherical or non-spherical, and may be polyurethane. The inner side of the substrate may be coated with a transparent conductive electrode (“TCO”). The conductive electrode can be formed of a transparent conductive material, such as indium tin oxide (“ITO”), fluorine-doped tin oxide (“FTO”), aluminum-doped zinc oxide (“AZO”), gallium-doped zinc oxide (“GZO”), indium-doped zinc oxide (“IZO”), aluminum gallium zinc oxide (“AGZO”), or indium gallium zinc oxide (“IGZO”). The sheet resistance of these TCOs must be less than 100 ohms / square, preferably less than 40 ohms / square, and even more preferably less than 10 ohms / square. The substrates can be spaced at a fixed distance from each other, for example with spacers of 10 μm to 400 μm, preferably 20 to 250 μm, and more preferably 150 μm, to form gaps in which the electrochromic composition is introduced.

[0117] Electrochromic solutions can be injected into the electrochromic device, for example, using a vacuum backfill method or a single-drop filling method. When using a vacuum backfill method to inject the solution into the unit, it is preferable to fabricate a unit with only one hole. Furthermore, in this case, when using the vacuum backfill method, the additives used preferably exhibit high boiling points, preferably having boiling points above 100°C. Additives with boiling points below 100°C are difficult to control.

[0118] As disclosed in WO 2006 / 013250, another device of the present invention includes an optical component having at least one transparent unit arranged juxtaposed in a direction parallel to its surface, each unit being tightly enclosed and containing the fluid, mesocrystalline, or gel host medium and the at least one compound of the present invention. Other devices according to the present invention may be devices comprising at least one compound of the present invention, as described in FR 2937154 or FR 2950710.

[0119] According to a third aspect, the present invention relates to the use of a mixture of a thickening polymer having a molecular weight of at least 50,000 g / mol, preferably at least 200,000 g / mol, and an additive having a molecular weight between 300 and 50,000 g / mol, in an electrochromic solution for reducing leakage current and color segregation as defined herein.

[0120] Example

[0121] The present invention will be further illustrated by the following non-limiting examples, which are given for illustrative purposes only and should not limit the scope of the appended claims.

[0122] Four electrochromic samples were prepared using four different electrochromic solutions to demonstrate the effect of a combination of two types of compound thickening polymers and additives on both leakage current / fading rate and viscosity.

[0123] Solution 1 is prepared by dissolving the following in propylene carbonate (98.96 wt%):

[0124] - Electrochromic reducing compound 10-methylphenthiazine (0.35 wt.%),

[0125] - Electrochromic oxidizing compound ethyl viologen diperchlorate (0.69 wt.%).

[0126] Solution 2 is prepared by dissolving the following in propylene carbonate (90.96 wt%):

[0127] - Electrochromic reducing compound 10-methylphenthiazine (0.35 wt.%),

[0128] - Electrochromic oxidizing compound ethyl viologen diperchlorate (0.69 wt.%)

[0129] - Thickening polymer agent PVAC (8 wt.%).

[0130] Solution 3 is prepared by dissolving the following in propylene carbonate (86.96 wt.%):

[0131] - Electrochromic reducing compound 10-methylphenthiazine (0.35 wt.%),

[0132] - Electrochromic oxidizing compound ethyl viologen diperchlorate (0.69 wt.%)

[0133] - Thickening polymer agent PVAC (12 wt.%).

[0134] Solution 4 is prepared by dissolving the following in propylene carbonate (70.96 wt.%):

[0135] - Electrochromic reducing compound 10-methylphenthiazine (0.35 wt.%),

[0136] - Electrochromic oxidizing compound ethyl viologen diperchlorate (0.69 wt.%)

[0137] -Thickening polymer agent PVAC (8 wt.%)

[0138] - Additive in liquid form: polyethylene glycol dibenzoate (PEGDB) (20 wt.%).

[0139] Propylene carbonate, ethyl viologen diperchlorate, and 10-methylphenthiazide are sold by Sigma-Aldrich.

[0140] The PVAC used was sold by Wacker Chemie under the name Vinnapas UW25FS. It has a molecular weight of 540,000 g / mol as measured by SEC, PS-standard.

[0141] The PEGDB used is a poly(ethylene glycol) dibenzoate with a molecular weight of 410 g / mol and a boiling point of 217 °C, sold by Sigma-Aldrich.

[0142] The tank was filled with electrochromic solutions 1 to 4 as described above at room temperature and atmospheric pressure. The unit was then placed vertically in the tank at atmospheric pressure, such that the opening was above the solution level. The unit comprises two facing inorganic glass substrates, the inner sides of which are coated with transparent conductive electrodes made of indium tin oxide (ITO). A gap was formed by using 150 μm spacers to maintain a fixed distance between the substrates. The edges of the unit were sealed with a UV-curable adhesive, leaving a 5 mm opening.

[0143] The cell containing the unit was placed in a vacuum dryer and evacuated to 0.5 mbar. During aeration of the cell under the introduction of an inert gas, the electrochromic formulation filled the entire volume of the gap through the openings. The openings were then sealed with a UV-curable adhesive to seal the unit. The electrical connections were made of two silver-plated copper wires and sealed to each ITO glass substrate with a silver-plated epoxy adhesive.

[0144] When the current typically stabilizes after one minute, the current consumption is measured with a standard ammeter.

[0145] Viscosity was measured using a Brookfield viscometer.

[0146] The sample was placed in a spectrophotometer, and the fading rate was measured from a higher visible transmittance value (Tv = 85%) to 10% transmittance (Tv) under activation. The applied voltage was 1.2V to achieve 10% transmittance.

[0147] Results regarding current consumption, fading rate, and viscosity are provided in Table 1.

[0148] Table 1

[0149]

[0150] Solution 1, containing only the solvent and the electrochromic compounds (methylphenthiazide and ethyl viologen diperchlorate), showed high current consumption. Segregation effects were visible after 1 hour.

[0151] PVAC was added to solutions 2 and 3 at 8 wt% and 12 wt%, respectively. Consequently, a decrease in leakage current and an increase in viscosity were observed, especially when PVAC was added at 12 wt%. In the latter case, a viscosity of 2500 cP was considered a very high value. In both cases, the segregation effect was eliminated and the current decreased.

[0152] In solution 4, segregation was eliminated by adding 8 wt% PVAC and 20 wt% liquid PEGDB; compared with the sample in solution 3, current consumption decreased significantly with a moderate increase in viscosity. The addition of PEGDB increased the viscosity measured at 25 °C from 420 cP to 1000 cP.

[0153] Therefore, due to the synergistic effect obtained by using thickening polymers and additives, the solution 4 of the present invention achieves a good balance between leakage current / fading rate and viscosity.

Claims

1. An electrochromic solution comprising: - Solvent; - Thickening polymer agent having a molecular weight of at least 200,000 g / mol; - At least one additive having a molecular weight between 300 and 50,000 g / mol; - A redox chemical mixture dissolved in the solvent, the mixture comprising at least one electrochromic reducing compound and at least one electrochromic oxidizing compound, which colors in the presence of an applied voltage and fades to a colorless state in the absence of an applied voltage. in, The content of the additive is from 5 to 60 wt% relative to the total weight of the electrochromic solution, and the content of the thickening polymer agent is from 1 to 30 wt% relative to the total weight of the electrochromic solution.

2. The electrochromic solution according to claim 1, wherein, The solvent is selected from ethylene carbonate, propylene carbonate, γ-butyrolactone, γ-valerolactone, acetonitrile, propionitrile, benzyl nitrile, glutaronitrile, methylglutaronitrile, dimethylformamide, N-methylpyrrolidone, sulfolane, 3-methylsulfolane, methyl propionate, ethylene glycol, propylene glycol diacetate, propylene glycol methyl ether acetate, ionic liquids, and mixtures thereof.

3. The electrochromic solution according to claim 1 or 2, wherein, The thickening polymer is a vinyl acetate polymer.

4. The electrochromic solution according to claim 1, wherein, The additive is selected from ester derivatives of benzoic acid or ester derivatives of phthalic acid, or mixtures thereof.

5. The electrochromic solution according to claim 1, wherein, The additive is selected from ester derivatives of benzoic acid having formula (I) or (II). (I) (II) Wherein R1 and R2 are the same or different and are selected from H, unsubstituted or substituted alkyl, unsubstituted or substituted aryl, unsubstituted or substituted cycloalkyl. Where n is an integer ranging from 1 to 10, and Where m is an integer ranging from 1 to 10.

6. The electrochromic solution according to claim 5, wherein, The substituted alkyl group is either unsubstituted or substituted arylalkyl.

7. The electrochromic solution according to claim 5, wherein, The additive is selected from a list of ester derivatives of benzoic acid, comprising polypropylene glycol dibenzoate (PPGDB), polyethylene glycol dibenzoate (PEGDB), and mixtures thereof.

8. The electrochromic solution according to claim 7, wherein, The polypropylene glycol dibenzoate (PPGDB) is selected from dipropylene glycol dibenzoate (DPGDB) and tripropylene glycol dibenzoate (TPGDB).

9. The electrochromic solution according to claim 7, wherein, The polyethylene glycol dibenzoate (PEGDB) is selected from diethylene glycol dibenzoate (DEGDB) and triethylene glycol dibenzoate (TEGDB).

10. The electrochromic solution according to claim 1, wherein, The additive is selected from a list of ester derivatives of phthalic acid, comprising bis(2-ethylhexyl phthalate) (DEHP), diisononyl phthalate (DINP), dioctyl phthalate (DNOP), diisodecyl phthalate (DIDP), dipropylheptyl phthalate (DPHP), di-2-ethylhexyl terephthalate (DOTP or DEHT), and mixtures thereof.

11. The electrochromic solution according to claim 1, wherein, The additives are selected from a list of diol derivatives.

12. The electrochromic solution according to claim 11, wherein, The diol derivative is selected from polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, polyethylene glycol diepoxide, polypropylene glycol diacrylate, polypropylene glycol dimethacrylate, polypropylene glycol diepoxide, and mixtures thereof.

13. The electrochromic solution according to claim 1, wherein, The additives are selected from a list of low molecular weight polymers.

14. The electrochromic solution according to claim 13, wherein, The low molecular weight polymer is selected from poly(methyl methacrylate) (PMMA), polyvinyl acetate (PVA), polyvinyl butyral (PVB), cellulose acetate butyrate (CAB), and mixtures thereof.

15. The electrochromic solution according to claim 1, wherein, The electrochromic solution contains at least two additives independently selected from the group consisting of ester derivatives of benzoic acid, ester derivatives of phthalic acid, diol derivatives, and low molecular weight polymers.

16. The electrochromic solution according to claim 1, wherein, The thickening polymer is a vinyl acetate polymer present in 5 to 15 wt% by weight relative to the total weight of the electrochromic solution, and the additive is a polypropylene glycol dibenzoate or polyethylene glycol dibenzoate present in 15 to 25 wt% by weight relative to the total weight of the electrochromic solution.

17. The electrochromic solution according to claim 1, wherein, The at least one electrochromic reducing compound is selected from ferrocene and its derivatives, phenoxazine and its derivatives, phenazine and its derivatives, N,N,N',N'-tetramethyl-p-phenylenediamine, phenothiazine and its derivatives; thioanthraene; and tetrathiofulvalene.

18. The electrochromic solution according to claim 17, wherein, The ferrocene and its derivatives are selected from ethyl ferrocene and tert-butyl ferrocene; the phenoxazine and its derivatives are N-benzylphenoxazine; the phenazine and its derivatives are 5,10-dihydrophenazine; the phenothiazine and its derivatives are selected from 10-methylphenothiazine and isopropylphenothiazine.

19. The electrochromic solution according to claim 1, wherein, The at least one electrochromic oxidizing compound is selected from alkyl viologen, aryl viologen, arylalkyl viologen, alkylaryl viologen, or anthraquinone, and their derivatives.

20. An electrochromic device comprising a solution according to any one of claims 1 to 19.

21. The electrochromic device according to claim 20, wherein, The electrochromic device is selected from optical products.

22. The electrochromic device according to claim 21, wherein, The optical products are selected from optical lenses, optical filters, attenuators, windows, sun visors, goggles, mirrors, and displays.

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