Image display device

An image display device which comprises a cell container, at least a pair of electrodes, and an electrically responsive electrochromic medium accomodated in said cell container, said electrochromic medium comprising a complexon, a redox reactive organic substance, Fe.sup.+2 ion and at least one metal ion which is (a) other than a Fe.sup.+2 ion (b) other than an Fe.sup.+3 ion and (c) other than an alkali metal ion, wherein said complexon is a member selected from the group consisting of:

• (1) an aminocarboxylic acid compound containing 1 to 3 aminocarboxylic acid groups represented by the following formula (I) ##STR9## wherein R.sub.1 represents hydrogen, methyl or hydroxyphenyl and n is 1 or 2;
• (2) an aminocarboxylic acid compound containing 1 to 2 aminocarboxylic acid groups represented by formula (I) above and 1 to 2 aminocarboxylic acid groups represented by the following formula (II):
• N--(CR.sub.1 H).sub.n --COOH (II)
• wherein R.sub.1 and n have the same meaning as in formula (I);
• (3) an aminocarboxylic acid compound containing an aminocarboxylic acid group represented by the following formula (III):
• ##STR10## wherein R.sub.1 and n have the same meaning as in formula (I);
• (4) an aminocarboxylic acid compound containing 2 aminocarboxylic acid groups represented by the following formula (IV):
• N--(CR.sub.1 H).sub.n --COOH (IV)
• wherein R.sub.1 and n mean the same as in formula (I);
• (5) an aminocarboxylic acid compound selected from the group consisting of ##STR11## (6) nitrogen, phosphorus and arsenic homologues thereof containing 1 to 2 groups represented by the following formula (V):
• A--(CH.sub.2).sub.n --B
• (V)
• wherein n is 1 or 2, A represents N, P or As and B represents --COOH, ##STR12## with the proviso that B is not --COOH when A is N;
• (7) nitrogen, phosphorus and arsenic homologues thereof containing 1 or 2 groups represented by the following formula (VI):
• ##STR13## wherein n, A and B mean the same as in formula (V);
• (8) nitrogen, phosphorus and arsenic homologues thereof containing 1 group represented by the following formula (VII):
• ##STR14## wherein n, A and B mean the same as in formula (V);
• and (9) mixtures thereof.