in an amount of 30 to 70 by weight all of 34 34 and 34 parts 34 given hereinafter are by weight especially 40 to 60 based on the cpes binder and that the organic acidic substance be used in an amount of 100 to 400 especially 150 to 350 based on the cpes binder known additives may be added in known amounts so as to improve various properties of the heat sensitive recording layer for example a white pigment such as titanium dioxide or a filler such as clay or calcium carbonate may be incorporated so as to improve the whiteness of the recording layer or increase the volume of the recording layer furthermore animal vegetable and mineral waxes such as paraffin wax and carnauba wax fatty acids and their derivatives such as stearic acid various soaps and fatty acid amides and synthetic waxes such as polyethylene wax polypropylene wax and polyethylene glycol may be incorporated so as to adjust the recording sensitivity alkanol amines such as triethanol amine and other organic bases may be incorporated so as to prevent coloration of the background background coloration a water resistance improver and a defoaming agent may be incorporated if desired though in the present invention it is ordinarily unnecessary to use such additives a coating.