Heat-sensitive recording material

Claim 1

In a black color developing heat-sensitive recording material comprising a base sheet and a color developing layer formed on at least one surface of the base sheet, said color developing layer including colorless or light-colored chromogenic material and acceptor which is reactive with said chromogenic material to develop a black color, an improvement that at least 60% by weight of said chromogenic material comprises at least two kinds of black color developing fluoran compounds having the same blackish hue and having the general formula ##STR5## where each R 1 , R 2 , R 3 and R 4 represents hydrogen, alkyl, alicyclic, aryl or aralkyl, each of which may have at least one substituent selected from the group consisting of halogen, alkyl, halogenated alkyl, cyanoalkyl, alicyclic, aryl, aralkyl, hydroxyl, alkoxyl, phenoxyl, acyl, carboxyl, alkoxycarbonyl, amino, substituted amino, cyano and nitro, R 1 may cooperate with R 2 to form a heterocyclic ring and R 3 may cooperate with R 4 to form a heterocyclic ring; R 5 represents hydrogen, halogen, alkyl, halogenated alkyl, cyanoalkyl, alkoxyl, aralkyl or substituted amino; R 6 represents hydrogen, halogen, alkyl, halogenated alkyl, cyanoalkyl or aralkyl; R 5 may cooperate with R 6 to form an aromatic ring; X represents halogen, alkyl, halogenated alkyl, cyanoalkyl or alkoxyl; Y represents halogen, alkyl, alicyclic, halogenated alkyl, cyanoalkyl, alkoxyl, aralkyl, aryl, acyl, amino, substituted amino or nitro; Y may form an aromatic ring together with the benzene ring to which Y is attached; l is zero or an integer of 1 to 2 and m is zero or an integer of 1 to 4, and the amount of each of said black color developing fluoran compounds is not larger than 90% by weight of the total amount of said black color developing fluoran compounds.