Heat-sensitive color-forming recording material and process for preparation thereof

Abstract

Disclosed is a heat-sensitive color-forming recording material which comprises a recording layer comprising a particulate phenolic color developer and a particulate leuco pigment, which are dispersed in a binder independently from each other, wherein the phenolic color developer and/or leuco pigment is present in the form of compatible solid particles with a substantially inactive organic solid medium having a melting or softening point lower than that of the phenolic color developer and/or leuco pigment and said organic solid medium is present in said compatible solid particles in an amount .[.2 to 250 times as large as.]. .Iadd.of 0.2 to 250% by weight, based on .Iaddend.the amount of the phenolic color developer and/or leuco pigment on the weight base. This heat-sensitized color-forming recording material is highly sensitive without substantial increase of the fog density.

What I claim is: 
     
       1. A heat-sensitive color-forming recording material which comprises a recording layer comprising a particulate phenolic color developer and a particulate leuco pigment, which are dispersed in a binder independently from each other, wherein the phenolic color developer and/or leuco pigment is present in the form of compatible solid particles with a substantially inactive organic solid medium selected from the group consisting of sterically hindered phenol compounds, said organic solid medium having a melting or softening point lower than that of the phenolic color developer and/or leuco pigment and said organic solid medium is present in said compatible solid particles in an amount .[.2 to 250 times as large as.]. .Iadd.of 0.2 to 250% by weight, based on .Iaddend.the amount of the phenolic color developer and/or leuco pigment on the weight base. 
     
     
       2. A recording material as set forth in claim 1, wherein the organic solid medium is present in an amount of 5 to 100% by weight based on the phenolic color former and/or leuco pigment. 
     
     
       3. A recording material as set forth in claim 1, wherein the number average particle size of the compatible solid particles is 0.1 to 3 microns. 
     
     
       4. A recording material as set forth in claim 1, wherein the binder is a water-soluble or water-dispersible binder. 
     
     
       5. A recording material as set forth in claim 1, wherein the recording layer contains the leuco pigment and the phenolic color former at a weight ratio of from 1/2 to 1/40 and the amount of the leuco pigment is 2 to 30% by weight based on the total recording layer. 
     
     
       6. A recording material as set forth in claim 1 wherein the organic solid medium is a sterically hindered phenol selected from the group consisting of 2,6-di-tert-butyl-p-cresol, 2,2-methylene-bis(4-ethyl-6-tertbutylphenol), 2-hydroxy-4-methoxybenzophenone, phenyl salicylate, p-tert-butyl salicylate and 2-(2'-hydroxy-5'-methylphenyl)-benzotriazole.