Thermosensitive recording material and use thereof

#This is a national stage of PCT application No. PCT/EP02/01756, filed on Feb. 20, 2002. Priority is claimed on that application and on the following application: Country: Germany, Application No.: 101 08982.1, Filed: Feb. 23, 2001.

#1. Field of the Invention

#The invention relates to a thermosensitive recording material including a substrate, a thermosensitive recording layer containing color formers and color acceptors, and a protective layer formed on the recording layer; and use thereof as a ticket.

#The invention is further explained below with reference to the accompanying figures, wherein:

#FIG. 1 shows the schematic structure of the thermosensitive recording material according to the invention in cross section; and

#FIG. 2 shows a plan view of the thermosensitive recording material according to the invention, cut to form a travel coupon.

#The thermal printing head triggering the color-forming reaction of the color formers with the color acceptors in the thermosensitive recording layer causes melting of the waxy components in the recording layer. In order to avoid adhesion of these waxy components, as a melt, to the thermal printing head, it is preferable to form an intermediate layer containing a pigment or a pigment mixture between the thermosensitive recording layer and the substrate, whereby the pigments of this intermediate layer effect absorption of the melt. It is preferred that the pigments of the intermediate layer have an oil absorption of at least 80 cm3/100 g, and more preferably of 100 cm3/100 g, determined according to Japanese standard JIS K 5101. Because of a large absorption reservoir that exist in its cavities, calcined kaolin has proven particulary useful. In numerous experiments, it has been found that it is advantageous to choose, in the intermediate layer, pigments having higher oil absorption than in the “spot” coating, i.e. the solid and localized coating printed on the protective layer. Since the air in the cavities of the pigments of the intermediate layer is a good heat insulator, an intermediate layer formed in this manner acts as a heat reflection layer, with the result that the thermosensitivity of the recording material, and hence the printing speed in the thermal printer, can be increased. Furthermore, such an intermediate layer can make a positive contribution to the leveling of the substrate surface, with the result that the amount of coating slip, which has to be applied for the thermosensitive recording layer is reduced. The formation of an intermediate layer having a mass per unit area in the range of from 5 to 20 g/m2, and preferably between 7 and 10 g/m2, is particularly advantageous.

#A coating slip, as proposed in EP-B-0 909 242, is suitable for the formation of the protective layer for the novel recording material of the present invention. Such a protective layer combines high resistance to the environment with outstanding printability by the wet offset process. Furthermore, the protective layer can be relatively economically produced and applied as a single layer.

#In order to support the cancelability of the novel recording material of the present invention in localized areas and to ensure that only as thin a print coat of the “spot” coating as possible need be applied, which is appropriate for increased resolution of the heat-induced protective images, the following conditions have proven particularly advantageous: the pigment of the protective layer contains one or more inorganic pigments, and at least 80% by weight are formed from a highly purified bentonite prepared under alkaline conditions, the binder of the protective layer consists of one or more water-insoluble, self-crosslinking acrylic polymers, the binder/pigment ratio in the protective layer is in the range between 7:1 and 9:1, the crosslinking agent/binder ratio in the protective layer is greater than 1:5 and preferably between 1:5 and 1:7 and the protective layer has a smoothness of at least 900 Bekk seconds.