Hitherto, a heat-sensitive recording material which utilizes a coloring reaction of a color former and a color developer which forms a color upon contact with the color former and provides a color image by contacting both coloring materials by the action of heat is well known.
Such heat-sensitive recording materials are comparatively inexpensive and can be used on a recording equipment that is compact and requires fairly easy maintenance. Because of these advantages, heat-sensitive recording materials are extensively used as recording media in a wide range of applications including facsimile equipments and various types of computers. One major problem with heat-sensitive recording materials is, however, their low resistance to fingerprints or solvents; if the recording layer comes in contact with a sebum of human being or a solvent, the color density of characters to be attained is decreased or an unwanted coloration ("background fog") occurs.
With a view to solving this problem, several methods have been proposed; in one method, a heat-sensitive recording layer is coated with an aqueous emulsion of a resin having film-forming properties and resistance to chemicals (Japanese Patent Application (OPI) No. 128347/79); and in another method, a heat-sensitive recording layer is coated with a water-soluble high molecular weight compound such as polyvinyl alcohol (Japanese Utility Model Application (OPI) No. 125354/81). The term "OPI" as used herein means "unexamined published application". However, the methods so far proposed either suffer from additional problems or find themselves incapable of achieving the intended results to satisfactory levels. For instance, in the method in which an aqueous resin coating is applied to the heat-sensitive recording layer, the temperature for drying has to be limited to a certain level in order to avoid unwanted coloration of the recording layer due to high-temperature drying, whereby curing of the resin layer inevitably becomes insufficient for preventing its sticking to a recording head during the recording. In order to avoid this problem, a method in which a heat-sensitive recording layer is coated with a resin component capable of curing upon exposure to electron beams and the coated resin component is cured upon exposure to electron beams is proposed. However, the resulting heat-sensitive recording material is still unsatisfactory in terms of preservability of recorded images. In addition, there may also be problems that the electron beam-curable resin layer causes coloration of the heat-sensitive recording layer just after it has been coated or causes fading of recorded images.
Attaching heat-sensitive recording materials to commercial goods has recently become a widespread practice, and in order to enhance the aesthetic appeal of the recording materials to thereby increase their commercial value as labels, it is desirable that the recording materials have either a high gloss or matted surface characteristics. This requirement is not fully met by the recording layer of existing heat-sensitive recording materials unless they are provided with an overcoat layer. However, the gloss attained by coating a heat-sensitive recording layer directly with an electron beam-curable resin layer as described above is not high enough to provide an increased commercial value for the product.