Stencil printing ink

The present invention relates to a stencil printing ink and, in particular, to a stencil printing ink that is suitable for use in a rotary digital stencil printing machine.

As the sheetfed printing ink, a water-in-oil (W/O) type emulsion ink has been generally used conventionally. W/O type emulsion inks have the function of suppressing changes in ink composition and physical properties even if the printing inks within the printing machine is in contact with the atmosphere when the printing machine is allowed to stand in a nonoperating state. That is, water, which is an inner phase component of the emulsion ink, is covered by oil, which is an outer phase component, and evaporation of water is therefore suppressed.

Various improvements have been carried out in order to improve the drying properties on printed materials; for example, an ultraviolet curing type ink for stencil printing that is dried and fixed by irradiation with ultraviolet rays is known. Furthermore, a water-based ink for offset printing ink has been developed from the viewpoint of environmental protection and safety, and a stencil printing method in which penetration of a water-based ink into paper is enhanced by adding a base to a printed surface immediately after printing is known. 

However, when a drying method involving a chemical reaction is used, it is necessary to employ irradiation equipment for the curing energy, coating equipment for a reaction solution, energy therefor, etc., and it is also necessary for the ink to contain expensive starting materials. 

It is therefore an object of the present offset printing inks to provide a stencil printing ink that enables the volume of ink transferred to a substrate to be controlled regardless of the level of viscosity of the ink, thereby enabling a detailed image to be printed, and that enables the drying properties on printed material to be improved without using special means, equipment, energy, etc. such as the application of heat, light, or a reactive material; and a stencil printing method employing the stencil printing inks.