Phthalide derivatives and recording system utilizing the same

Claim 1

A recording system which utilizes the color forming reaction between a colorless chromogenic material and an electron accepting acid reactant material, comprising a base sheet and a chromogenic material which comprises at least one phthalide derivative having the following formula: ##STR10## wherein at least one of R 1 , R 2 , R 3 , R 4 , R 5 and R 6 radicals is an alkoxyalkyl having 3 to 8 carbon atoms; an unsaturated alkyl having 3 to 9 carbon atoms, tetrahydrofurfuryl; tetrahydropyran-2-methyl; an aralkyl represented by the following formula ##STR11## in which n is 0, 1 or 2, R 7 is hydrogen or an alkyl having 1 to 4 carbon atoms and R 8 is hydrogen, halogen, an alkyl having 1 to 4 carbon atoms or an alkoxyl having 1 to 4 carbon atoms, and when n is 0 and R 7 is hydrogen, R 8 is halogen or an alkoxy having 1 to 4 carbon atoms; an alkyl having 2 to 8 carbon atoms and having phenoxy group which may be substituted by at least one selected from the group consisting of halogens, alkyls having 1 to 4 carbon atoms, and alkoxyls having 1 to 4 carbon atoms; or a halogenated alkyl having 1 to 8 carbon atoms; and each of the other ones of said radicals is hydrogen; an alkyl having 1 to 8 carbon atoms which may be substituted by at least one halogen; a cycloalkyl having 5 to 12 carbon atoms; an alkoxyalkyl having 3 to 8 carbon atoms; an unsaturated alkyl having 3 to 9 carbon atoms; tetrahydrofurfuryl; tetrahydropyran-2-methyl; an aralkyl which may be substituted by at least one selected from the group consisting of halogens, alkyls having 1 to 4 carbon atoms and alkoxyls having 1 to 4 carbon atoms; an aryl which may be substituted by at least one selected from the group consisting of halogens, alkyls having 1 to 4 carbon atoms and alkoxys having 1 to 4 carbon atoms; or an alkyl having 2 to 8 carbon atoms and having phenoxy group which may be substituted by at least one selected from the group consisting of halogens, alkyls having 1 to 4 carbon atoms, and alkoxyls having 1 to 4 carbon atoms; or one or two pairs of R 1 and R 2 , R 3 and R 4 , and R 5 and R 6 may form morpholino, pyrrolidino, piperidino or hexamethyleneimino group together with the adjacent nitrogen atom.