EP0068635A1 — Electrochromic display device

Claim 1

Independent Claim 107 words

An electrochromic display device comprising: two substrates (17, 20; 117, 120 1 217,220; 317, 320); a plurality of electrodes (18,21; 118,121; 218; 319) formed on one or both substrates, at least one of said electrodes being a display electrode (18; 118; 218; 318)which is coated with a layer of an electrochromic material (19; 119; 219; 319) and, an electrolyte (23; 123; 223; 323) held between said substrates, characterised in that the electrochromic material is a layer of the iron (III) hexacyanoferrate (II) salt which, in operation, is reversibly changed in colour through electrochemical oxidation and reduction reactions induced between said electrodes so as to provide a display.

Claim 2

Dependent Claim 107 words

An electrochromic display device comprising: two substrates (17, 20; 117, 120 1 217,220; 317, 320); a plurality of electrodes (18,21; 118,121; 218; 319) formed on one or both substrates, at least one of said electrodes being a display electrode (18; 118; 218; 318)which is coated with a layer of an electrochromic material (19; 119; 219; 319) and, an electrolyte (23; 123; 223; 323) held between said substrates, characterised in that the electrochromic material is a layer of the iron (III) hexacyanoferrate (II) salt which, in operation, is reversibly changed in colour through electrochemical oxidation and reduction reactions induced between said electrodes so as to provide a display.

Claim 3

Dependent Claim 37 words

An electrochromic display device as claimed in claim 1 characterised in that the electrochromic material is electrodeposited as an intimately adhering blue insoluble solid film from a solution having Fe(III) ion and hexacyanoferrate (III) ion dissolved therein.

Claim 4

Dependent Claim 137 words

An electrochromic display device as claimed in claim 1 or 2 characterised in that the electrochromic material (19; 119; 219; 319) is a-layer of a complex salt whose composition is represented by formula (1) when it is in a ground state exhibiting a first colour,by formula (2) when it is in a reduced state exhibiting a second colour, and by formula (3) when it is in an oxidised state exhibiting a third colour, where formula (1) is formula (2) is formula (3) is wherein M + is a monovalent cation, X ℓ- is an ℓ-valent anion, ℓ is 1 or 2, m is O or a positive integer not greater than 5, n is O or a positive integer, x and y are positive integers, and where, ℓ, m, x and y satisfy all the following inequalities

Claim 5

Dependent Claim 75 words

An electrochromic display device as claimed in claim 3 characterised in that said electrochromic material (19,119,219 319) is an insoluble coating in which the composition of formula (1) is represented by Fe III 4 [Fe II (CN) 6 ] 3 , the composition of formula (2) is represented by M + 4FeII 4 [Fe II (CN) 6 ] 3 , and the composition of formula (3) is represented by Fe III4[Fe III (CN) 6 ]

Claim 6

Dependent Claim 37 words

An electrochromic display device as claimed in claim 3 or 4 characterised in that the monovalent cation, M + is a potassium ion, rubidium ion, cesium ion or ammonium ion, and the electrolyte contains the same cation.

Claim 7

Dependent Claim 59 words

An electrochromic display device as claimed in any of claims 3 to 5 characterised in that the anion, X ℓ- is a chloride ion, nitrate ion, perchlorate ion, tetrafluoroborate ion, or hexafluorophosphorate ion when ℓ is equal to 1, or a sulphate ion or carbonate ion when ℓ is equal to 2, and the electrolyte contains the same anion.

Claim 8

Dependent Claim 23 words

An electrochrcmic display device as claimed in any preceding claim characterised in that the electrolyte (23,123,223,323) has a pH between 3 and 5.

Claim 9

Dependent Claim 60 words

An electrochromic display device as claimed in any preceding claim characterised in that one of said electrodes is a counter electrode (21,121) formed on the substrate (20,121) which is opposite to the substrate (17,117) on which said at least one display electrode (18,118) is formed, said counter electrode (21,121) having a layer of a salt of iron (III) hexacyanoferrate (II).

Claim 10

Dependent Claim 46 words

An electrochromic display device as claimed in claim 8 characterised in that the counter electrode (21,121) comprises a layer of a salt of iron (III) hexacyanoferrate (II) which is electrodeposited as an insoluble solid film from a solution containing iron (III) ion and hexacyanoferrate (III) ion.

Claim 11

Dependent Claim 93 words

lO. An electrochromic display device comprising: a pair of substrates, a plurality of electrodes formed on said substrates, a display electrode selected from said plurality of electrodes, said display electrode coated with a layer of an electrochromic material consisting of a salt of iron (III) hexacyanoferrate (II) and an electrolyte held between said pair of substrates, wherein said layer of the iron (III) hexacyanoferrate (II) salt on said display electrode is reversibly changed in colour through electrochemical oxidation and reduction reaction induced between said plurality of electrodes so as to provide a display.

Claim 12

Dependent Claim 93 words

lO. An electrochromic display device comprising: a pair of substrates, a plurality of electrodes formed on said substrates, a display electrode selected from said plurality of electrodes, said display electrode coated with a layer of an electrochromic material consisting of a salt of iron (III) hexacyanoferrate (II) and an electrolyte held between said pair of substrates, wherein said layer of the iron (III) hexacyanoferrate (II) salt on said display electrode is reversibly changed in colour through electrochemical oxidation and reduction reaction induced between said plurality of electrodes so as to provide a display.

Electrochromic display device

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