Thermal stenciling device

Claim 1

A thermal stenciling device comprising a thermal head constructed of a plurality of heat generating elements arranged in line in a main-scanning direction, the heat generating elements being adapted to be pressed against a thermoplastic resin film bonded to a porous carrier constituting a heat-sensitive stencil paper and be relatively moved in a sub-scanning direction perpendicular to the main-scanning direction to form a plurality of dot perforations through the thermoplastic resin film of the heat-sensitive stencil paper by heat of the heat generating elements; wherein each of the heat generating elements of the thermal head has a size to be decided by the following four formulas: A/a:B/b=1:α(α=0.6 to 1.0); A/a=β(β=0.8 to 1.2); A+C=Pa; and B+C=Pb; where, A: length of each perforation in the main-scanning direction; a: length of each heat generating element in the main-scanning direction; B: length of each perforation in the sub-scanning direction; b: length of each heat generating element in the sub-scanning direction; α: ratio of perforation rate in the sub-scanning direction to perforation rate in the main-scanning direction; β: the perforation rate in the main-scanning direction; C: length of a gap as an imperforated portion between the adjacent dot perforations in the main-scanning direction and the sub-scanning direction; Pa: dot pitch in the main-scanning direction; and Pb: dot pitch in the sub-scanning direction.

Claim 3

A method for determining a size for heat generating elements of a thermal head used for creating stencils, comprising the steps of: determining a desired length of perforation in each of a main-scanning direction and a sub-scanning direction; establishing a gap defining a non-perforated portion between adjacent dot perforations in the main-scanning direction and the sub-scanning direction; generating a dot pitch in the main scanning direction and a sub-scanning direction; and determining a length of the heat generating elements in the main scanning direction and the sub-scanning direction to satisfy the relationship that the length of the perforation in the main-scanning direction divided by the length of the heat generating element in the main scanning direction is in a first range of 0.8 to 1.2 and the ratio of the length of the perforation in the sub-scanning direction divided by the length of the heat generating element in the sub-scanning direction is in a range of 0.6 to 1.0 of a value determined from the first range.

Claim 4

A method for determining a size for heat generating elements of a thermal head used for creating stencils, comprising the steps of: determining a desired length of perforation in each of a main-scanning direction and a sub-scanning direction; establishing a gap defining a non-perforated portion between adjacent dot perforations in the main-scanning direction and the sub-scanning direction; generating a dot pitch in the main scanning direction and a sub-scanning direction; and determining a length of the heat generating elements in the main scanning direction and the sub-scanning direction to satisfy the relationship that the length of the perforation in the main-scanning direction divided by the length of the heat generating element in the main scanning direction is in a first range of 0.8 to 1.2 and the ratio of the length of the perforation in the sub-scanning direction divided by the length of the heat generating element in the sub-scanning direction is in a range of 0.6 to 1.0 of a value determined from the first range.