e g novolac polyvinyl phenols carboxy substituted polymers etc typical examples of these polymers are described in de a 4 007 428 de a 4 027 301 and de a 4 445 820 specific examples of switchable image recording layers that are suitable for use in the present embodiment can be found in ep 924 102 wo92 09934 ep 652 483 u s pat no 4 081 572 ep 200 488 and ep 924 065 according to a second class of preferred embodiments the image recording layer comprises hydrophobic thermoplastic polymer particles in a cross linked hydrophilic binder preferably the hydrophilic binder is a homopolymer or copolymer of vinyl alcohol acrylamide methylol acrylamide methylol methacrylamide acrylic acid methacrylic acid hydroxyethyl acrylate hydroxyethyl methacrylate or maleic anhydride vinylmethylether copolymers the hydrophilicity of the co polymer or co polymer mixture used is the same as or higher than the hydrophilicity of polyvinyl acetate hydrolyzed to at least an extent of 60 percent by weight preferably 80 percent by weight polyvinyl alcohol is highly preferred the crosslinking agent is preferably a tetraalkyl orthosilicate crosslinking agents such as hydrolyzed tetraethyl orthosilicate and hydrolyzed tetramethyl orthosilicate the amount of tetraalkyl orthosilicate crosslinking agent is at least 0 2 parts by weight per part by weight of hydrophilic co polymer preferably between 0 5 and 5 parts by weight preferably 1 5 part by weight the hydrophilic layer of the heat recording material preferably also contains substances that increase the mechanical strength and the porosity of the layer for this purpose colloidal silica may be.