Abstract: Europium compounds represented by the general formula (1) and water-base ink compositions containing the same: [wherein X is an optionally substituted aromatic or heterocyclic group: Y is a fluorohydrocarbon group having 1 to 10 carbon atoms: Z1 to Z3 are each independently a hydrophilicity-imparting group: R1 to R3 are each a direct bond or a divalent hydrocarbon or heterocyclic group which may be substituted: n1 to n3 are each independently an integer of 0 to 2: and m1 to m3 are each independently an integer of 1 to 3, with the proviso that all of n1to n3must not be 0]. The compounds and the ink compositions are excellent in stability and safety, and emit red light by irradiation with ultraviolet light though they are substantially invisible in the visible light region. Thus, they are useful for prints which are to be read by a system having a sensor reading function with the need for hidden letters or security markings.

Abstract: A near-infrared absorbing filter which does not contain antimony, arsenic or the like and is excellent in heat resistance is disclosed. The near-infrared absorbing filter is characterized by containing a compound composed of a salt of cations obtained by oxidizing a substance represented by the formula (1) below and anions (X), which are alkylsulfonate ions having 1-8 carbon atoms that are necessary for neutralizing the cations and not substituted or may be substituted with a halogen atom, a lower alkyl group, a cyano group, or a hydroxy group. (1) (in the formula (1), rings A and B may have a substituent, and R1-R8 independently represent a substituted or non-substituted (C1 to C8) alkyl group, cycloalkyl group, alkenyl group or aryl group.

Abstract: An aqueous ink composition containing a europium compound (A) represented by the following formula (1), a binder (B) and an aqueous medium (C). (wherein X represents an aromatic ring group or a heterocyclic ring group that may have a substituent, Y represents a fluorinated hydrocarbon group having 1-10 carbon atoms, and M represents an alkali metal or an alkaline earth metal.

Abstract: A mixture of two or more diimonium salts or aminium salts obtained by oxidizing one or more compounds represented by the general formula (1); near-infrared absorption filters characterized by containing the mixture; and optical information recording media characterized by containing the mixture in the recording layer: (1) wherein A and B may have additional substituents; R1 and R2 attached to terminal nitrogen atoms of tetrakis(aminophenyl)-phenylenediamine skeleton are different from each other and each substituted or unsubstituted alkyl having 1 to 8 carbon atoms, cycloalkyl, alkenyl, or aryl; and m and n are integers of 0 to 8 satisfying the relationship: m+n=8.

Abstract: A near-infrared absorbing filter, characterized in that it contains at least one compound represented by the following formula (1): 1

Abstract: Europium compounds represented by the general formula (1) and water-base ink compositions containing the same: 1

Abstract: The present invention relates to an aminium salt or diimonium salt compound that is appropriate for use, for examples, in an optical recording medium to get the good characteristics in regeneration and storage stability as well as an infrared ray screening filter to get the excellent light fastness and heat fastness; and the use thereof. The aminium salt or diimonium salt compound comprises an aminium cation represented by the formula (1) as described below or a diimonium cation represented by the formula (2) as described below: (In the formula, m is an integer of 1 or 2; the two nitrogen atoms (quaternary nitrogen atoms in Formula (2)) bound to the ring A in Formula (1) or Formula (2) bind to the four B phenyl groups to whose 4-positions the optionally substituted four amino groups are substituted; and at least one of said four amino groups has a cyanoalkyl group as the substituent) with an anion.