Method for producing an electrochromic device

This invention relates to a method for producing an electrochromic device.

An electrochromic device is generally produced by sealing the periphery, except for a portion thereof, of a pair of electrically conductive substrates, at least one of which is transparent, placed in a spaced-apart opposing relationship with each other so as to assemble a cell having an injection port formed by the unsealed portion and filling the inner space of the cell by charging through the port an electrolyte or the precursor thereof in a vacuum. The injection port of the cell is then sealed by filling and curing therein a photo-setting or thermosetting acrylic resin or epoxy resin adhesive.

However, such a method for sealing or closing the port requires a step of removing the electrolyte adhered around the injection port prior to filling the adhesive. If the electrolyte is not removed completely, the adhesive can not seal the port sufficiently. Furthermore, the above sealing method fails to obtain satisfactory sealing strength due to an insufficient cure of the adhesive caused by the contact thereof with the electrolyte.

Japanese Laid-Open Patent Publication Nos. 2-114237 and 6-250230 disclose a two-step sealing method to solve the foregoing problems.

Japanese Laid-Open Patent Publication No. 2-114237 discloses a method which comprises a primary sealing and a secondary sealing. In this method, first of all, there is prepared a cell having an opening formed in a selected portion of the peripheral edges of a pair of substrates in an opposing relation. After an electrolyte is charged through the opening, the primary sealing is conducted by coating an epoxy resin adhesive to the opening while an external pressure is vertically applied to the substrates, followed by releasing the pressure to allow the sealant to enter into the inside of the opening and cure therein. After a certain period of time, the secondary sealing is carried out by coating an epoxy resin adhesive on the peripheral edges of the substrate induding the primary sealed portion and allowing the adhesive to cure itself.

This method is recognized as being applicable to the production for a electrochromic device of a relatively small size. However, the method is not always suitable for the production for an electrochromic device of a relatively large size because the primary sealing requires the process of applying an extemal pressure onto the cell. Furthermore, this two-step sealing method is mainly focused on the injection port (opening) provided on the end surface of the cell. Therefore, when this method is employed for producing the large electrochromic device, there may arise a risk that the adhesive would peel off due to the stress applied to the sealing portion upon transportation of the device even though the sealing is completed in a satisfactory manner.

Japanese Laid-Open Publication No. 6-250230 proposes a method in which an electrolyte injection port is sealed with a radiation-cure type adhesive and then sealed with an epoxy resin adhesive so as to be overlapped with the former adhesive. However, with this method the above risk can not be removed because it also attempts to solve the above problem by providing the electrolyte injection port in the end surface of the cell.

An object of the invention is to provide a method for producing an electrochromic device whose which sealing portion of the electrolyte injection port is free from the peel off of the adhesive by arranging an electrolyte injection passage formed by a member which is made of a press-deformable material and adjusted in orientation so as to extend suitably from the port through the sealed edge of the opposed substrates, even upon being employed for the production of a large size electrochromic device on which stress would possibly applied during the transportation of the device.

Another object of the invention is to provide a method for producing an electrochromic device. The method can avoid completely the contact between an electrolyte and an adhesive to be used for sealing the electrolyte injection port and thus is also free from a risk that the curing reaction of the adhesive is hindered.

According to the invention, there is provided a method for producing an electrochromic device which comprises: <ul id="ul0001" list-style="none" compact="compact"><li>(a) a step of assembling a hollow cell constituting an electrochromic device by sealing together the entire peripheral edges of two electrically conductive substrates, at least one of which is transparent, disposed in a spaced-apart opposing relationship with each other and by providing at least a portion of the sealed edge with an opening, whose surroundings are formed by a press-deformable member, having a passage extending not perpendicular to the end surface of the opposed substrates:</li><li>(b) a step of vacuum-inserting an electrolyte or the precursor thereof through the opening into the cell;</li><li>(c) a step of closing the opening by pressing deformably the surroundings after completion of the injection;</li><li>(d) a step of sealing the dosed opening with an adhesive.</li></ul>

Figs. 1 and 2 are partial plan views from the transparent substrate of the electrochromic device produced by the inventive method and show each a shape of the opening before and after injecting an electrolyte, respectively.

An electrically conductive substrate used for the inventive method means literally a substrate functioning as an electrode. The electrically conductive substrate may be that of which substrate itself is electrically conductive or that of which is not electrically conductive but has an electrode layer disposed on the surface contacting the layer of an electrolyte.

Such an electrically conductive substrate may be iron, copper, silver, aluminum, tin, lead, gold and zinc and alloys thereof. The non-electrically conductive substrate may be any type of substrate as long as it has a smooth surface. Specific examples are substrates made of a material such as plastics (synthetic resin), glass, wood and stone.

The electrochromic device produced by the invention includes a pair of such electrically conductive substrates one of which is necessarily transparent. Such an electrically conductive transparent substrate may be produced by laminating an electrode layer on a transparent substrate. The transparent substrate may be colored or colorless glass as well as colored or colorless plastic (synthetic resin). Eligible plastics for this purpose are polyethylene terephthalate, polyamide, polysulfone, polyether sulfone, polyether etherketone, polyphenylene sulfide, polycarbonate, polylmide, polymethyl methacrylate and polystyrene.

The term "transparent" used herein designates optical transmission ranging from 10 to 100 %. The substrate used for the invention may be flat or curved and may be deformable by stress as long as it has a smooth surface at room temperature.

It is preferred that the electrode layer to be laminated on the non-electrically conductive substrate is transparent. It is requisite that at least the electrode layer to be laminated on the transparent substrate is transparent. Eligible for the electrode layer are a thin film of metal such as gold, silver, chrome, copper and tungsten or a metal oxide such as ITO (In₂O₃-SnO₂), tin oxide, silver oxide, zinc oxide and vanadium oxide.

The thickness of the electrode is selective within the range of usually 10 to 1,000, preferably 50 to 300 nm. The surface resistance of the electrode may be selected suitably but usually in the range of 0.5 - 500, preferably 1 - 50 Ω/sq.

No particular limitation is imposed on the formation method of the electrode layer. Any suitable conventional methods may be selected depending upon the metal and metal oxide constituting the electrode. In general, the formation of the electrode layer is carried out by vacuum evaporation, ion plating, sputtering and a sol-gel method. In any case, the formation of the electrode should be conducted While maintaining the temperature of the substrate within the range of 100 - 350 °C.

The electrode layer may be partially provided with an opaque electrode-activator in order for the purpose of imparting oxidation-reduction capability and increasing electric double layer capacitance. In this case, if it is necessary to maintain the transparency of the electrode, the optical transmission of the whole electrode is kept within the range of 10 - 100 %.

Electrode activators eligible for the purpose of the invention include a metal such as copper, silver, gold, platinum, iron, tungsten, titanium and lithium, an organic material having oxidation-reduction capability such as polyaniline, polythiophen, polypyrrole and phthalocyanine, a carbon material such as active carbon and graphite and a metal oxide such as V₂O₅, WO₃, MnO₂, NiO and Ir₂O₃ and mixtures thereof. These electrode activators may be integrated to the electrode with a binder resin.

The opaque electrode activator may be applied onto an electrode by forming over an ITO transparent electrode a composition comprising an active carbon fiber, graphite and an acrylic resin in the shape of stripes or by forming on a thin-film of gold (Au) a composition comprising V₂O₅, acetylene black and butyl rubber in a meshed pattern.

The cell for the electrochromic device according to the invention is produced by opposing the two electrically conductive substrates (one of which is transparent), in a spaced-apart relationship with each other and sealing the inner peripheral edges of the opposed substrates. If the electrically conductive substrate is one obtained by laminating an electrode layer thereon, the electrode layer is placed to face the inside of the cell. The space between the opposed substrates is within the range of usually 30 - 1,000, preferably 200 - 500µm. The cell used for the invention is provided in at least a portion of the sealed inner peripheral edge with an opening, whose surroundings are formed by a member of a material which is deformable by press, having a passage extending not perpendicular to the end surface of the opposed substrates.

Needless to mention, an electrochromic device contains an electrochromic material. Such an electrochromic material may be mixed in an electrolyte layer or formed into the electrochromic layer separately from the electrolyte layer. The electrochromic layer may be arranged anywhere the inside of the cell. In general, prior to the assembly of the cell, the electrochromic layer may be arranged on at least one or both of the electrode layers on the electrically conductive substrates. When the electrochromic material is mixed into the electrolyte layer, there may be employed a method in which to inject the mixture of an electrolyte or the precursor thereof and the electrochromic material into the cell.

The electrochromic material may be exemplified by substances colored, bleached or discolored by electrochemical oxidation or reduction such as MO₂O₃, Ir₂O₃, NiO, V₂O₅, WO₃, biologen, polythiophene, polyaniline, polypyrrole, metal phthalocyanine and ferrocene.

The electrochromic layer may be formed solely from the electrochromic material or may be formed from the electrochromic material and the matrix component thereof, the former being preferred. The electrochromic layer has a thickness in the range of usually 10nm - 1µm, preferably 50 - 800nm.

There may be employed any conventional method for forming the electrochromic layer such as vacuum evaporation, ion-plating, sputtering, electrolytic polymerization, dip coating and spin coating.

No particular limitation imposed on a sealant used for sealing the peripheral edges of the opposed electrically conductive substrates as long as it can seal up the device so as to isolate the Interior thereof from its surroundings and so as to prevent a component such as moisture, oxygen and carbon monoxide adversely effecting the performances of the device from permeating into the interior of the device. Therefore, eligible sealants are exemplified by synthetic resins including polyester such as polyethylene terephtalate, polyamide, polysulfone, polyether sulfone, polyether etherketone, polyphenylene sulfide, polycarbonate, polyimide, polymethyl methacrylate, polystyrene, tricellulose acetate, polymethylpentene, polysiloxane, polyethylene, polypropylene, polycellulose acetate, phenolic resin, urea resin, epoxy resin, polyvinyl acetate, polyvinyl acetal, polyvinyl alcohol, acrylic and methacrylic esters, cyanoacrylate and polyamide; natural rubbers; and synthetic rubbers such as isoprene rubber, butadiene rubber, styrene-butadiene rubber, butyl rubber, ethylene·propylene rubber, chloropylene rubber, chlorosulfonated polyethylene, nitrile rubber, urethane rubber, polysulfide rubber, acrylic rubber, epichlorohydrin rubber, silicone rubber, fluorine rubber and hydrogenated nitrile rubber.

Alternatively, hardening resins are also eligible for the sealant. There is no particular limitation to the hardening resins and thus various hardening type resins are eligible such as those cured by heat and electromagnetic ray. Eligible hardening resins are phenolic resin, urea resin, epoxy resin, polyvinyl acetate, polyvinyl acetal, polyvinyl alcohol, acrylic and methacrylic esters, cyanoacrylate and polyamide. These may be used singular or in combination. Further alternatively, these resins may be modified by adding fillers. Among these, particularly preferred are an epoxy resin and an acrylic-modified epoxy resin. Preferred acrylic-modified epoxy resins are those containing 0.01 - 0.3 mol of acrylic residue per mol of epoxy residue, preferably 0.05 - 0.2 mol of acrylic residue per mol of epoxy residue.

When the peripheral edges of the opposed electrically conductive substrates are sealed, it is preferred to use a spacer for adjusting the width of the space between the substrates. The spacer needs to be non-electrically conductive but may have sheet-, sphere-, fiber- or bar- like shape.

There may be employed any suitable method for sealing the electrically conductive substates such as the following methods: <ul id="ul0002" list-style="none" compact="compact"><li>(1) Inserting the sealing material having been processed and formed in conformity with the shape of the electrically conductive substrates therebetween;</li><li>(2) Coating the above-mentioned hardening resin paste in a desired shape over the surface of the substrate using a known printing method;</li><li>(3) Coating the sealant over the surface of the substrate; and</li><li>(4) Forming the sealant discharged from a nozzle into a suitable pattem on the substrate by moving the nozzle.</li></ul>

Among these, particularly preferred is method (4).

The sealant may be applied to either one or both of the substrates.

When the hardening resin is applied to the substrate, it is hardened after the substrates are laminated. Needless to mention, the hardening is effected depending on the resin used.

If a thermal-hardening resin is used, there may be used such a resin hardening at room temperature. If a thermal-hardening resin requiring heat to be hardened is used, it is selected from the resins which harden at a temperature ranging from room temperature to 150 °C, preferably from room temperature to 100 °C. The period of time required for hardening is selected to an extent that electrochromic characteristics are not adversely effected, preferably from the range Within 24 hours, more preferably from the range within one hour.

If a photo-hardening resin is employed, there may be used various types light sources as long as they initiate the photo-hardening. Such a light source may be exemplified by low-, high- and ultrahigh- voltage mercury lumps, a xenon lump and an incandescent lamp and laser beams. The hardening of the resin may be conducted by exposing the entire surfaces of the device after being applied with the resin to light such that the resin is hardened simultaneously. Alternatively, the photo-hardening may be effected in a step by step manner by scanning a gathered spot light over the resin, for example, by moving a light source or using a photoconductive material such as an optical fiber. This may be repeated more than twice.

The cell used for the invention is provided in at least a portion of the sealed inner peripheral edge with an opening, whose Surroundings are formed by a member of a deformable material by press, having a passage extending not perpendicular to the end surface of the opposed substrates.

No particular limitation is imposed on materials for the member forming the opening. In general, eligible materials are those which are free from problems relating to compatibility with and aherability to the sealant and the above-mentioned sealants among which are deformable by press, the latter being preferred.

Specific examples of such materials are natural rubbers, isoprene rubber, butadiene rubber, styrene butadiene rubber, butyl rubber, ethylene propylene rubber, chloropylene rubber, chlorosulfonated polyethylene, nitrile rubber, urethane rubber, polysulfide rubber, acrylic rubber, epichlorohydrin rubber, silicone rubber, fluorine rubber and hydrogenated nitrile rubber.

Any suitable method may be employed for the formation of the opening. For instance, in the case where the same material is used for the member and the sealant, it is possible to form the opening in a desired shape Simultaneously with application of the sealant to the peripheral edges of the opposed substrates. In the case where the member is a different material from that of the sealant, the opening may be formed upon or after application of the sealant.

After completion of the injection of an electrolyte or the precursor thereof into the cell, the opening is dosed by deformably pressing a portion of the member forming the opening and passage from the outside of the cell. The member thus functions as a sealing member as well. The opening is usually sealed in a two step manner, a primary step of which is carried out by pressing a rubber forming the surroundings of the opening and passage and a secondary step of which is carried out by sealing the primary sealed portion. The sealant used for the secondary step is not limited and thus may be selected from various types of sealants such as those of photo-, thermo-, room temperature- and electro beam-setting types. As a matter of course, there may be used acrylic-, epoxy- and silicone-resin adhesives as well as other types of adhesives such as phenolic resin, urea resin, epoxy resin, polyvinyl acetate, polyvinyl acetal, polyvinyl alcohol, acrylic and methacrylic esters, cyanoacrylate and polyamide. These may be used singular or in combination. Alternatively, these may be modified or added with fillers.

In view of solvent resistance, the epoxy resin is found to be particularly superior. An acrylic-modified epoxy resin of photo-setting type is preferred. Preferred for such an acrylic-modified epoxy resin are those having 0.01 - 0.3 mol, preferably 0.05 - 0.2 mol of acrylic residue per mol of epoxy residue.

The thermo setting of the adhesive for the secondary sealing may be conducted by using various types of heat sources such as ovens, infrared heaters, electric heaters and surface type heat generators at a temperature ranging from room temperature to 150 °C, preferably room temperature to 100 °C. The time required for the thermo-setting is not restricted but is usually within 24 hours, preferably within one hour.

The photo-setting may be conducted by using various types of light sources such as low-, high- and ultrahigh- voltage mercury vapor lamps, a xenon lamp, an incandescent lamp and laser beams. The photo-setting of the adhesive may be conducted by exposing evenly the entire surfaces of the device to light after being applied with the adhesive. Alternatively, a step by step manner may be employed Which is effected by scanning a gathered spot light over the device, for example, by moving a light source or using a photoconductive material such as an optical fiber or a mirror. Practically preferred are methods which to use a 100W - 1KW ultrahigh voltage mercury vapor lamp or a xenon-mercury vapor lamp. Among these, preferred are methods in which to guide the light from a light source of a 200 - 500 W xenon-mercury vapor lamp using an optical fiber.

Description is now made to the shape of the opening with referring to Figs.1 and 2.

In the illustrated embodiment, the peripheral edges of the opposed electrically conductive substrates (10) are sealed primarily with a butyl rubber and secondarily with an epoxy resin adhesive of thermo setting type to seal around the primary sealed portion. As shown in Fig. 1, the opening (13) used for injecting an electrolyte or the precursor thereof has a passage (14) extending not perpendicular to the end surface of the opposed substrates. The opening as well as the passage is formed by a member which is deformable by press. Although the passage takes a "Z"-like shape in this embodiment, it may be oriented in a slanted relationship with the end surface of the opposed substrates.

According to the invention, an electrolyte or the precursor thereof is vacuum-injected into the cell through the opening thereof having the passage extending not perpendicular to the end surface of the opposed substrates. Hereinafter, the descriptions are made with respect to the electrolyte and the precursor thereof.

Although the electrolyte used for the electrochromic device produced by the inventive method may be any type of electrolytes as long as they can color and bleach the electrochromic material contained in the device, preferred are those having an ion conductivity of more than 1 x 10^-7 S/cm at room temperature. The electrolyte may be of liquid, gel or solid. Solid electrolytes are particularly preferred for the purpose of the invention.

Eligible liquid electrolytes are those dissolving a supporting electrolyte such as salts, acids and alkalis in a solvent. Any suitable solvents may be used as long as they can dissolve the supporting electrolyte. Particularly preferred are those having polarity. Specific examples of such a solvent indude water and organic polar solvents such as methanol, ethanol, propylene carbonate, ethylene carbonate, dimethylsulfoxide, dimethoxyethane, acetonitrile, r-butyrolactone, r-valerolactone, sulforan, 1,3-dioxane, N,N-dimethylormamide 1,2-dimethoxyethane and tetrahydrofuran. Preferred are propylene carbonate, ethylene carbonate, dimethylsulfoxide, dimethoxyethane, acetonitrile, r-butyrolactone, sulforan, 1,3-dioxolane, N,N-dimethylformamide, 1,2-dimethoxyethane and tetrahydrofurun. These may be used singular or in combination.

Although not restricted, salts used as the supporting electrolyte may be alkali metal salts, inorganic ion salts such as alkali earth metal salts, quatemary ammonium salts and cyclic quatemary ammonium salts. Specific examples of such salts indude alkali metal salts of lithium, sodium or potassium such as LiClO₄, LiSCN, LiBF₄. LiAsF₀, LiCF₃SO₃, LiPF₆, Lil, Nal, NaSCN, NaClO₄, NaBF₄, NaAsF₆, KSCN and KCI, quatemary ammonium salts or cydic quatemary ammonium salts such as (CH₃)₄NBF₄, (C₂H₅)₄NBF₄, (n-C₄H₉)₄NBF₄, (C₂H₅)₄NBR, (C₂H₅ )₄NClO₄ and (n-C₄H₉)₄NClO₄ and mixtures thereof.

Acids used as the supporting electrolyte may be exemplified by inorganic acids and organic acids which indude sulfuric acid, hydrochloric acid, phosphoric acid, sulfonic acid and carboxylic acid.

Alkalis used as the supporting electrolyte indude sodium hydroxide, potassium hydroxide and lithium hydroxide.

The gelatinized-liquid electrolyte may be those which are gelatinized or made to be viscous by adding a polymer or a gelatinizer to the above-mentioned liquid electrolytes.

Preferred examples of such a polymer are polyacrylonitrile, carboxymethylcellulose, polyvinyl chloride, polyethylene oxide, polyurethane, polyacrylate, polyamide, polyacrylamide, cellulose, polyester. polypropyleneoxide and nafion.

Preferred examples of the gelatinizer are oxyethylenemethacrylate, oxyethyleneacrylate, urethaneacrylate, acrylamide and agar-agar.

The gelatinized-liquid electrolyte is sandwiched between the opposed electrically conductive substrates by injecting into the cell the mixture of h the precursor monomer of a polymer or the precursor of the gelatinizer and a liquid electrolyte then and then polymerizing or gelatinizing the mixture.

There is no particular limitation to the solid electrolyte if It is solid at room temperature and ion conductive. Preferred examples of such solid electrolyte are polyethyleneoxide, the polymer of Oxyethylenemethacrylate, nafion, polystylene sulfonate, Li₃N, Na-β-Al₂O₃ and In(HPO₄)₂H₂O. Particularly preferred are polymeric solid electrolytes derived from polymerization of a polyethyleneoxide-based compound, an oxyalkyleneacrylate-based compound or a urethaneacrylate-based compound used as the main component of the precursor.

A first example of such a polymeric solid electrolyte is one obtained by solidifying a composition (hereinafter referred to as Composition A) which is used as a precursor and comprises an organic polar solvent, a supporting electrolyte and a urethaneacrylate represented by the formula <chemistry id="chem0001" num="0001"><img file="EP0947876A2_D0001.tif" /></chemistry> wherein R¹ and R² may be the same or different and are each a group of formula (2), (3) or (4), R³ and R⁴ may be the same or different and are each a C1-C_20, preferably C₂-C₁₂ divalent hydrocarbon residue, Y is selected from a polyether unit, a polyester unit, a polycarbonate unit and the mixed unit thereof and n is an integer of 1-100.

Formulae (2), (3) and (4) are represented by <chemistry id="chem0002" num="0002"><img file="EP0947876A2_D0002.tif" /></chemistry><chemistry id="chem0003" num="0003"><img file="EP0947876A2_D0003.tif" /></chemistry> and <chemistry id="chem0004" num="0004"><img file="EP0947876A2_D0004.tif" /></chemistry> respectively wherein R⁵, R⁶ and R⁷ may be the same or different and are each a hydrogen atom or a C₁-C₃ alkyl group and R⁸ is a C₁-C₂₀ preferably C₂-C₈ organic residue of divalent through quatervalent. Such organic residues may be a hydrocarbon residue such as alkyltolyl, alkyltetratolyl and alkylene of the formula <chemistry id="chem0005" num="0005"><img file="EP0947876A2_D0005.tif" /></chemistry> Wherein R⁹ is a C₁-C₃ alkyl group or hydrogen, p is an integer of 0-6 and if p is greater than 2 the groups of R⁹ may be the same or different.

The hydrocarbon residue may be a group part of which hydrogen atoms are substituted by an oxygen-containing hydrocarbon group such as a C₁-C₆ preferably C₁-C₃ alkoxy group and a C₆-C₁₂ aryloxy group. Specific examples of group R⁸ in formulae (2) thorough (4) are those represented by the following formulae:    ―CH₂ CH₂― <chemistry id="chem0006" num="0006"><img file="EP0947876A2_D0006.tif" /></chemistry>    ―CH₂―CH₂―CH₂―CH₂― <chemistry id="chem0007" num="0007"><img file="EP0947876A2_D0007.tif" /></chemistry>

Each of the divalent hydrocarbon residues represented by R³ and R⁴ in formula (1) is exemplified by a divalent chain-like hydrocarbon group, an aromatic hydrocarbon group and an alicyclic-containing hydrocarbon group. Specific examples of the chain-like divalent hydrocarbon group are those represented by formulae (6) through (8) <chemistry id="chem0008" num="0008"><img file="EP0947876A2_D0008.tif" /></chemistry><chemistry id="chem0009" num="0009"><img file="EP0947876A2_D0009.tif" /></chemistry> and <chemistry id="chem0010" num="0010"><img file="EP0947876A2_D0010.tif" /></chemistry> wherein R¹⁰ and R¹¹ may be the same or different and are each a phenylene group, a phenylene group having an alkyl subsutituent, a cycloalkylene group and a cycloalkylene group having an alkyl substituent, R¹², R¹³, R¹⁴ and R¹⁵ may be the same or different and are each a hydrogen atom or a C₁-C₃ alkyl group and q is an integer of between 1 and 5.

Specific examples of the groups R³, and R⁴ in formula (1) are those represented by the following formulae         CH₂CH₂CH₂CH₂CH₂CH₂     (9) <chemistry id="chem0011" num="0011"><img file="EP0947876A2_D0011.tif" /></chemistry><chemistry id="chem0012" num="0012"><img file="EP0947876A2_D0012.tif" /></chemistry><chemistry id="chem0013" num="0013"><img file="EP0947876A2_D0013.tif" /></chemistry><chemistry id="chem0014" num="0014"><img file="EP0947876A2_D0014.tif" /></chemistry><chemistry id="chem0015" num="0015"><img file="EP0947876A2_D0015.tif" /></chemistry> and <chemistry id="chem0016" num="0016"><img file="EP0947876A2_D0016.tif" /></chemistry>

In formula (1), Y indicates a polyether unit, a polyester unit, a polycarbonate unit and mixed unit thereof. Each of these units is represented by the following formulae : <chemistry id="chem0017" num="0017"><img file="EP0947876A2_D0017.tif" /></chemistry><chemistry id="chem0018" num="0018"><img file="EP0947876A2_D0018.tif" /></chemistry><chemistry id="chem0019" num="0019"><img file="EP0947876A2_D0019.tif" /></chemistry> and <chemistry id="chem0020" num="0020"><img file="EP0947876A2_D0020.tif" /></chemistry> wherein R¹⁵ through R²¹ may be the same or different and are each a C₁-C₂₀, preferably C₂-C₁₂ divalent hydrocarbon residue, C₁-C₆ being particularly preferred for R¹⁹, m is an integer of 2-300, preferably 10-200, r is an integer of 1-300, preferably 2-200, s is an integer of 1-200, preferably 2-100, t is an integer of 1-200, preferably 2-100 and u is an integer of 1-300, preferably 10-200.

R¹⁵ through R²¹ are preferably straight or branched alkylene groups among which methylene, ethylene, trimethylene, tetramethylene, pentamethylene, hexamethylene and propylene groups are preferred for R¹⁶, and ethylene and propylene groups are preferred for R¹⁶, R ¹⁷ and R¹⁹ through R²¹.

Each unit represented by formulae (a) through (d) may be a copolymer of the same or different units. In other words, if there exist a plurality of the groups of each R¹⁶ through R²¹, the groups of each R¹⁶_, R¹⁷, R¹⁸, R¹⁹, R²⁰ and R²¹ may be the same or different. Preferred examples of such copolymers include a copolymer of ethylene oxide and a copolymer of propylene oxide.

In formula (1), n is preferably an integer of 1 - 50, more preferably 1 - 20. The urethaneacrylate of formula (1) has a molecular weight in the range of 2,500 - 30,000, preferably 3,000 - 20,000,

The urethaneacrylate has preferably 2 - 6, more preferably 2 - 4 functional groups per molecule.

The urethaneacrylate may be prepared by any suitable conventional methods.

There is no limitation to the organic polar solvent contained in Composition (A) as long as it has a polarity and can dissolve the electrolyte. Preferred are propylene carbonate, ethylene carbonate, butylene carbonate, Υ -butyrolactone, sulfolane, 1,3-dioxane, N,N-dimethylformami de, 1,2-dimethoxyethane, acetnitrile and tetrahydrofuran. These solvents may be used singular or in combination. The organic polar solvent is added in an amount of 100-1,200, preferably 200 - 900 weight parts per 100 parts of the urethaneacrylate. Too less amount of adding the organic polar solvent results in insufficient ion conductivity, while too much amount causes a reduction in mechanical strength.

The supporting electrolyte contained in Composition (A) is selected depending on the usage of the device. Generally, the above-described liquid electrolytes are preferably used. The supporting electrolyte should be added in an amount of 0.1-30, preferably 1-20 weight percent of the organic polar solvent.

The first example of the solid polymeric electrolyte is essentially obtained by solidifying Composition (A) (precursor) composed of the urethaneacrylate, the organic polar solvent and the supporting electrolyte. If necessary, Composition (A) may be added with any suitable components as long as they are not obstructive to the achievement of the purpose of the invention. Such components may be crosslinkers and photo- and thermal polymerization.

Composition (A) is injected through the opening provided in the peripheral edge the electrically conductive substrates disposed, facing each other to from a cell and then is cured in a conventional manner such that the first example of the solid polymeric electrolyte is sandwiched between the electrically conductive substrates. The term "curing" used herein designates a state where the component is cured with the progress of polymerization (polycondensation) or crosslinking and thus the composition does not flow at room temperature. The urethaneacrylate has the basic structure in the form of network by curing.

A second example of the polymeric solid electrolyte is obtained by solidifying a composition (hereinafter refereed to as Composition (B)) which is used as a precursor and comprising an organic polar solvent, a supporting electrolyte, a monofunctional acryloyl-modified polyalkylene oxide and/or a polyfunctional acryloyl-modified polyalkylene oxide.

The mono-functional acryloyl-modified polyalkylene oxide is represented by the formula <chemistry id="chem0021" num="0021"><img file="EP0947876A2_D0021.tif" /></chemistry> wherein R²², R²³, R²⁴ and R²⁵ may be the same or different and are each hydrogen and an alkyl group having 1 - 5 carbon atoms and n is an integer of greater than 1.

Specific examples of such alkyl group indude methyl, ethyl, i-propyl, n-propyl, n-butyl, t-butyl and n-pentyl. Preferred for R²², R²³ and R²⁴ are hydrogen and a methyl group. Preferred for R²⁵ are hydrogen, a methyl and ethyl group.

n in formula (16) is an integer greater than 1, usually between 1 and 100, preferably 2 and 50, more preferably 2 and 30.

Specific examples of compounds represented by formula (16) are those having 1-100, preferably 2-50, more preferably 1-20 oxyalkylene units, such as methoxypolyethylene glycol methacrylate, methoxypolypropylene glycol methacrylate, ethoxypolyethylene glycol methacrylate, ethoxypolypropylene glycol methacrylate, methoxypolyethylene glycol acrylate, methoxypolypropylene glycol acrylate, ethoxypolyethylene glycol acrylate, ethoxypolypropylene glycol acrylate and mixtures thereof.

If n is greater than 2, the compound may be those having different oxyalkylene units, that is, copolymerized oxyalkylene units which for instance have 1-50, preferably 1-20 oxyethylene units and 1-50, preferably 1-20 oxypropylene units. Specific examples of such compounds are (ethylene · propylene) glycol methacrylate, ethoxypoly ( ethylene · propylene) glycol methacrylate, methoxypoly (ethylene·propylene) glycol methacrylate, methoxypoly (ethylene propylene) glycol acrylate, ethoxypoly methoxypoly (ethylene·propylene) glycol acrylate and mixtures thereof.

Eligible polyfunctional acryloyl-modified polyalkylene oxide for Composition (B) is a bifunctional acryloyl-modified polyalkylene oxide or a polyfunctional acryloyl-modified polyalkylene oxide having more than three functional groups. The bifunctional acryloyl-modified polyalkylene oxide is represented by the formula <chemistry id="chem0022" num="0022"><img file="EP0947876A2_D0022.tif" /></chemistry> wherein R²⁶, R²⁷, R²⁸ and R²⁹ are each hydrogen and a C₁ - C₅ alkyl group and m is an integer greater than 1. The polyfunctional acryloyl-modified polyalkylene oxide having more than three functional groups is represented by the formula <chemistry id="chem0023" num="0023"><img file="EP0947876A2_D0023.tif" /></chemistry> wherein R³⁰, R³¹ and R³² are each hydrogen and a C₁ - C₅ alkyl group, p is an integer greater than 1, q is an integer of 2 - 4 and L is a connecting group of valence indicated by q.

If R²⁶, R²⁷, R²⁸ and R²⁹ are alkyl groups, such alkyl groups may be methyl, ethyl, i-propyl, n-propyl, n.butyl, t-butyl, t-butyl and n-pentyl. Preferred for R²⁶, R²⁷ , R²⁸ and R29 are hydrogen and a methyl group.

m in formula (17) is an integer greater than 1, usually 1-100, preferably 2-50, more preferably 2-30. Preferred examples of compounds of formula (17) are those having 1-100, preferably 2-50, more preferably 1-20 oxyalkylene units such as polyethylene glycol diacrylate, polypropylene glycol dimethacrylate, polyethylene glycol diacrylate, polypropylene glycol dimethacrylate and mixtures thereof.

If m is greater than 2, the compounds of formula (17) may be those having different oxyalkylene units, that is, polymerized oxyalkylene unit having 1 - 50, preferably 1-20 oxyethylene units and 1-50, preferably 1-20 oxypropylene units, such as poly(ethylene · propylene)glycol dimethacrylate, poly(ethylene · propylene)glycol diacrylate and mixtures thereof .

If R³⁰, R³¹ and R³² are alkyl groups, preferred are methyl, ethyl, i-propyl, n-propyl, n-butyl, t-butyl and n-pentyl groups. Particularly preferred for R³⁰, R³¹ and R³² are hydrogen and a methyl group.

p in formula (18) is an integer of usually between 1 and 100, preferably 2 and 50, more preferably 2 and 30.

q in formula (18) is a number of connecting group "L" and an integer between 2 and 4.

Connecting group "L" is a divalent, trivalent or quatravalent hydrocarbon group having 1-30, preferably 1-20 carbon atoms.

Such divalent hydrocarbon groups may be alkylene, arylene, arylalkylene, alkylarylene and hydrocarbon groups having those groups as the base skeleton. Specific examples of such hydrocarbon groups are those represented by the following formulae :         ―CH₂―         ―CH₂ CH₂― <chemistry id="chem0024" num="0024"><img file="EP0947876A2_D0024.tif" /></chemistry>    (Bz represents a benzene ring).

Such trivalent hydrocarbons groups may be alkyltryl, aryltryl, arylalkyltryl, alkylaryltryl and hydrocarbon groups having those groups as the base skeleton. Specific examples of such hydrocarbon groups are those represented by the following formulae: <chemistry id="chem0025" num="0025"><img file="EP0947876A2_D0025.tif" /></chemistry><chemistry id="chem0026" num="0026"><img file="EP0947876A2_D0026.tif" /></chemistry><chemistry id="chem0027" num="0027"><img file="EP0947876A2_D0027.tif" /></chemistry>

The quatravalent hydrocarbon group may be alkyltetraryl, aryltetraryl, arylalkyltetraryl, alkylaryltetraryl or hydrocarbon groups having those groups as the base skeleton. Specific examples are those represented by the following formulae <chemistry id="chem0028" num="0028"><img file="EP0947876A2_D0028.tif" /></chemistry>

Specific examples of compounds of formula (18) are those having 1-100, preferably 2-50, more preferably 1-20 of an oxyalkylene units such as trimethylolpropanetri (polyethylene glycol acrylate), trimethylolpropanetri (polyethylene glycol methaacrylate), trimethylolpropanetri (polypropylene glycol acrylate), trimethylolpropanetri (polypropylene glycol methaacrylate), tetramethylolmethanetetra(polyethylene glycol acrylate), tetramethylolmethanetetra (polyethylene glycol methaacrylate) , tetramethylolmethanetetra (polypropylene glycol acrylate), tetramethylolmethanetetra(polypropylene glycol methaacrylate) , 2,2-bis[4- (acryloxypolyethoxy)phenyl]propane, 2,2-bis[4-(methaacryloxypolyethox y)phenyl]propane, 2,2-bis[4- (acryloxypolyisopropoxy)phenyl]propane, 2,2-bis[4-(methaacryloxypolyisopropoxy)phenyl]propane and mixtures thereof.

If p is more than 2, compounds of formula (18) may be those having different oxyalkylene units, that is, polymerized oxyalkylene units having 1-50, preferably 1-20 of oxyethylene units and 1-50, preferably 1-20 oxypropylene units. Specific examples of such compounds Include trimethylolpropanetri(poly(ethylene·'propylene)glycol acrylate), trimethylolpropanetri(poly(ethylene·propylene)glycol methaacrylate), tetramethylolmethanetetra(poly(ethylene . propylene) glycol acrylate), tetramethylolmethanetetra(poly(ethylene . propylene)glycol methaacrylate) and mixtures thereof.

Needless to mention, there may be used the difunctional acryloyl-modified polyalkyleneoxide of formula (17) and the polyfunctional acryloyl-modified polyalkyleneoxide of formula (18) in combination. When these compounds are used in combination, the weight ratio of the compound of formula (17) to that of formula (18) is in the range between 0.01/99.9 and 99.9/0.01, preferably 1/99 and 99/1, more preferably 20/80 and 80/20. When the compound of formula (16) is used in combination with the compound of formula (17) or (18), the weight ratio therebetween is in the range of usually between 1/0.001 and 1/1, preferably 1/0.05 and 1/0.5.

The organic polar solvent and supporting electrolyte described with respect to Composition (A) are also eligible for Composition (B). The organic polar solvent should be added in an amount of 50-800, preferably 100-500 weight percent based on the total weight of the monofunctional acryloyl- modified polyalkyleneoxide and the polyfunctional acryloyl-modified polyalkyleneoxide.

The supporting electrolyte should be added in an amount of 1-30, preferably 3-20 weight percent based on the total Weight of the monofunctional acryloyl-modified polyalkyleneoxide and the polyfunctional acryloyl-modified polyalkyleneoxide.

If necessary, Composition (B) may be added with another components optionally as long as they do not bother the achievement of the purpose of the invention. Such components may be photopolymerization initiators or thermal polymerization initiators. These initiators should be added in an amount of 0.05-5, preferably 0.01-3 weight percent based on the total weight of the monofunctional acryloyl-modified polyalkyleneoxide and the polyfunctional acryloyl-modified polyalkyleneoxide.

Composition (B) is injected through the opening provided in the peripheral edge of the electrically conductive substrates disposed, facing each other to from a cell and then is cured in a conventional manner so that the second example of the solid polymeric electrolyte is sandwiched between the electrically conductive substrates. The term "curing" used herein designates a state where the monofunctional acryloyl-modified polyalkyleneoxide or the polyfunctional acryloyl-modified polyalkyleneoxide is cured with the progress of polymerization (polycondensation) or crosslinking and thus the composition does not flow at room temperature. In this case, the monofunctional acryloyl-modified polyalkyleneoxide or the polyfunctional acryloyl-modified polyalkyleneoxide has the basic structure in the form of network.

According to the invention, any of the above-described liquid, gelatinized and solid electrolytes is generally injected into the cell. However, needless to mention, an electrolyte other than the above-described electrolytes may be injected into the cell. The gelatinized- and solid- electrolytes are injected into the cell in the form of a precursor. As already described, the electrolyte or the precursor may be added with the electrochromic material beforehand. Upon the injection, there is selected a suitable method which can fill evenly the space between the two electrically conductive substrates with the electrolyte or the precursor. There is usually employed a vacuum injection method in which the hollow interior of the cell is evacuated so as to be ideally in vacuum and then the injection port (opening) of the cell is submerged into the liquid electrolyte or the precursor under atmospheric pressure such that the liquid electrolyte is supplied into the cell by utilizing the difference in pressure between the outside and inside of the cell.

Upon completion of the injection, before the precursor is gelatinized or solidified, the injection port (opening) of the cell is dosed or sealed. As shown Figs. 1 and 2; the injection port (13) is dosed or sealed by press-deforming the outer wall (15) of the passage (13) so as to abut against the inner wall (16) in a suitable manner.

After completion of dosing the injection port, it is washed to remove the electrolyte or the precursor thereof adhered around the port and then sealed with an adhesive.

According to the invention, since upon completion of the injection of the electrolyte or the precursor thereof, the passage forming a part of the injection port can be primarily sealed by press-deforming, the washing of the portion around the injection port can be washed completely prior to the secondary sealing. As a result, the adhesive is not adversely affected in capability by the electrolyte or the precursor thereof, resulting in an increase in the durability of the sealed portion. Furthermore, because the passage leading the electrolyte or the precursor thereof to the cell is oriented not perpendicular to the end surface of the opposed substrates, it is possible to avoid bubbles from entering into the cell via the passage after completing the injection.

The present invention will now be explained in further detail with reference to Examples, which are given only by way of illustration but are not intended for limiting the invention.

Example 1

Preparation of Counterelectrode for Electrochromic Device

A pasty active carbon was prepared by mixing 80 g of active carbon powder manufactured by KURARE under the trade name of YR17, 40 g of graphite manufactured by NIPPON KOKUEN SHOJI CO., LTD. under the trade name of USSP, 343 g of a silicone resin manufactured by NIPPON UNICAR CO., LTD. under the trade name of RZ7703 and 25 g of butyl cellosolve. On an ITO glass substrate (a transparent electrically conductive glass substrate produced by forming a layer having a thickness of 2,500 A on a glass by sputtering using an In₂O₃:Sn target) of 10 Ω/sq in electrical <i>surface</i> resistance, 2mm in thickness and 50cm x 50cm in size, the above-obtained active carbon paste was screenprinted to form a striped pattem; each stripe is 500 µm in width and 100 µm in height. The printed area was 20 % of the total area of the electrode layer. The printed active carbon was cured by heating at a temperature of 180°C for 90 minutes thereby obtaining a counterelectrode.

Preparation of Electrochromic Electrode for Electrochromic Device

On an ITO glass substrate of 10 Ω/sq in electrical surface resistance, 2mm in thickness and 50cm x 50cm in size, a 5,000 Å tungsten oxide film was deposited at room temperature under the condition of 10 - 30 Å/second to obtain an electrochromic electrode.

The counterelectrode substrate and the electrochromic electrode substrate were then placed in a 500 µm spaced apart opposing relationship with each other, followed by sealing the inner peripheral edges of the Opposed substrates and providing a portion of the sealed edges with an opening thereby producing a hollow cell. A butyl rubber of 5mm wide had been applied to the peripheral edges as a primary sealant for sealing the peripheral edges and a thermo-setting epoxy resin sealant of 5mm wide as a secondary sealant. The sealants were cured at 90°C for one hour. The opening was formed by a butyl rubber so as to have a "Z"-like shaped passage as shown in Fig. 1.

An electrolyte solution (1 mol/L concentration) containing a supporting electrolyte of LiClO₄ in Υ -butyrolactone solvent was deaerated and then charged through the opening into the hollow cell in vacuum. Upon completion of the injection of the electrolyte, the cell was maintained horizontally thereby confirming that no bubbles entered the cell via the passage. The opening and passage were primarily sealed by pressing the outer wall thereof so as to abut against the inner wall. After the removal of the electrolyte adhered around the sealed portion by washing with an ethanol, the sealed portion was coated with a photo-setting adhesive manufactured by THREE BOND under the trade name of 3025 and then exposed to a light of 4,000 mJ by a high voltage mercury vapor lamp such that the adhesive is cured and the bonding of the sealing portion was completed, thereby obtaining an electrochromic device.

The coloring and bleaching test was carried out to measure the change of optical density. First, an electrical voltage of 1.5 V was applied across the electrochromic device for 150 seconds so as to be negative at the electrochromic electrode with respect to the counterelectrode. The electrochromic device was uniformly colored in blue, and the change in optical density at the center of the device was 0.50.

Immediately after the 150-second coloration of the device, an electrical voltage of 1.0 V was in turn applied across the device for 60 seconds so as to be positive at the electrochromic electrode against the counterelectrode. The device was then bleached back to the colorless initial state.

The electrochromic device was left in an oven at a temperature of 65 °C and a humidity of 95% for 1,000 hours. The device was taken out from the oven and the peel off at the sealing portion was not observed.

The electrochromic device was placed on 5 cm³ of acrylic supporting members situated under the corners of the device so as to be deformed by its weight for one month. The peel off at the sealing portion was not observed.

Coloring and Bleaching Test

633nm of He-Ne laser beam having been expanded in diameter to 20mm by a beam expander was irradiated so as to pass through the center of the electrochromic device and the transmitted light was measured by using an Si photodiode. On applying an electrical voltage for coloration, the transmitted light intensity was measured every 5 seconds. If the transmitted light intensity at "t" second after the coloration voltage is applied is expressed by T(t), the change in optical density is defined by the following equation:<maths id="math0001"><math display="block"><mrow><mtext>Change in Optical Density = log[T Bleach / T(t)] (log is common logarithms)</mtext></mrow></math><img file="EP0947876A2_D0029.tif" /></maths>

Example 2

A photo-setting type electrolyte solution was prepared by admixing 20 weight percent of methoxytetraethylene glycol methacrylate and 0.02 weight percent of DAROCURE 1173 to an electrolyte solution (1 mol/L concentration) containing an LiClO₄ electrolyte in a solvent of γ-butyrolactone.

The procedures of charging the electrolyte and sealing primarily the opening (injection port) of Example 1 were followed except for using the above-obtained electrolyte. After completion of the secondary sealing with use of a photo-setting type adhesive, the electrolyte in the cell was cured by a light of 20 J in illumination from a high voltage mercury vapor lamp thereby providing an electrochromic device.

The coloring and bleaching test was carried out to measure the change of optical density. First, an electrical voltage of 1.5 V was applied across the electrochromic device for 150 seconds so as to be negative at the electrochromic electrode with respect to the counterelectrode. The electrochromic device was uniformly <i>colored</i> in blue, and the change in optical density at the center of the device was 0.48.

Immediately after the 150-second coloration of the device, an electrical voltage of 1.0 V was in turn applied across the device for 60 seconds so as to be positive at the electrochromic electrode against the counterelectrode. The device was then bleached back to the colorless initial state.

The electrochromic device was left in an oven at of 65 °C and a humidity of 95% for 1,000 hours. The device was taken out from the oven and the peel off at the sealing portion was not observed.

Example 3

A cell was prepared by following the procedures of Example 1 except that the space between the substrates was changed to 200 µm. An electrochromic device was prepared by charging the electrolyte used in Example 1 in vacuum into the cell obtained above and closing the passage in the same manner of the primary and secondary sealing of Example 1.

The coloring and bleaching test was carried out to measure the change of optical density. First, an electrical voltage of 1.5 V was applied across the electrochromic device for 150 seconds so as to be negative at the electrochromic electrode with respect to the counterelectrode. The electrochromic device was uniformly colored in blue, and the change in optical density at the center of the device was 0.50.

Immediately after the 150-second coloration of the device, an electrical voltage of 1.0 V was in turn applied across the device for 60 seconds so as to be positive at the electrochromic electrode against the counterelectrode. The device was then bleached back to the colorless initial state.

The electrochromic device was left in an oven at 65 °C and a humidity of 95% for 1,000 hours. The device Is taken out from the oven and the peel off at the sealing portion was not observed.

Comparative Example 1

A cell of the same in size as that produced in Example 1 was produced. Instead of making an opening having a passage extending not perpendicularly with respect to the end surface of the opposed substrates, this cell has an opening formed by omitting a part of sealing applied to the peripheral edges of the two opposing substrates.

An electrolyte solution (1 mol/L concentration) containing an electrolyte of LiClO₄ in γ-butyrolactone solvent was charged in vacuum into the above-obtained cell. When the cell was placed horizontally, it was observed that bubbles entered the hollow space of the cell through the injection port. After removing the bubbles and washing the charging port with an ethanol, it was coated with a photo-setting adhesive manufactured by THREE BOND under the trade name of 3025 and then exposed to a light of 4,000 mJ in illumination from a high voltage mercury vapor lamp thereby sealing the port.

The electrochromic device was left in an oven at a temperature of 65 °C and a humidity of 95% for 400 hours. The device is taken out from the oven and the peel off was observed at the sealing portion of the port.

Comparative Example 2

An electrochromic device produced by following the procedures of Comparative Example 1 was placed on 5 cm³ of acrylic supporting members situated under the comers of the device so as to be deformed by its weight for one week. The peel off was observed at the portion of the sealing for the port.