Heat-sensitive stencil paper

Details Heat-sensitive stencil paper Heat-sensitive stencil paper

1991-12-06

1993-11-16

Ryan, Patrick J.

Stock material or miscellaneous articles

Structurally defined web or sheet

Discontinuous or differential coating, impregnation or bond

428211, 4283044, 4283113, 4283117, 428336, 428342, 428913, B32B 300

Patent

active

052622215

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The present invention relates to a heat-sensitive stencil paper which is suited for thermal heads, and to a porous tissue paper to be used therefor. More particularly, it relates to a heat-sensitive stencil paper which is suited for the preparation of a stencil using a high-speed and high-resolution stencilizer printer, an apparatus consisting of an integrated combination of a stencilizer and a printer.


PRIOR ART

In recent years, there has been developed the technology of stencilizing a stencil paper by using a heat element, such as a thermal head, and the technology has been in practical use. In addition, there have appeared on the market stencilizer printers, which are consisted of an integrated combination of a stencilizer and a printer designed to achieve a higher printing speed and a higher resolution.
In general, a heat-sensitive stencil paper to be used for stencilizer printers is composed of an ink permeating support on which is adhered a thermoplastic film.
As supports to be used for heat-sensitive stencil papers, there have been proposed various porous tissue papers, including those prepared from natural fibers of, e.g., kozo (paper mulberry), mitsumata (Edgeworthia papyrifara), Manila hemp or the like; those prepared from synthetic fibers, for example, rayon, vinylon or polyester fibers; and those prepared from a mixture of natural and synthetic fibers. However, in products actually available on the market at present are used tissue papers prepared from fibers of Manila hemp, polyester or a mixture of hemp and polyester. With the expansion of the use of automatic stencilizers or automatic stencilizer printers in recent years, heat-sensitive stencil papers consisting mainly of Manila hemp have come to be used most widely due to their excellent transportability.
Among known stencilization processes are included so-called xenon flash lamp perforation method and so-called thermal head perforation method. In the former method, a stencil paper and an original is superposed in such a manner that the marginal portions in the peripherals of the stencil paper are fixed, and then infrared rays are irradiated thereon, whereby the heat sensitive film present on the porous tissue paper of the stencil paper shrinks to form perforations in accordance with the image of the original. In the latter method, a thermal head is allowed to contact with the surface of the heat-sensitive film of the stencil paper and activated to generate heat at places to be image-wise perforated, whereby the positions of the film contacted with the thermal head instantaneously shrink, forming perforations.
The thermal head perforation method is now becoming more popular than the xenon flash lamp perforation method since it is less susceptible to undesirable generation of perforations in background areas.
However, heat-sensitive stencil papers using a porous tissue paper prepared from natural fibers consisting mainly of Manila hemp suffer from shives characteristic of natural fibers. Knot areas present in a heat-sensitive could be hardly perforated. Even in cases where knot areas could be somehow perforated, perforations formed in the areas do not permeate sufficient quantities of ink upon stencil printing, thus forming unprinted white spots on printed products. Because of this, various proposals have been made to obtain knot-free porous tissue papers from natural fibers. However, the quality of natural fibers, such as Manila hemp, varies widely depending on the site of cultivation, weather, and the like. The production of such tissue papers requires a complicated production control and hence suffers from the problem of low productivity. It is very difficult, so long as natural fibers are used, to completely solve the problem of knots, like the cases where synthetic polyester fibers are employed.
On the other hand, heat-sensitive stencil papers using a porous tissue paper prepared from polyester fibers can be almost free from the problem of knots, but suffer from the problems that their rigidity is insufficien

REFERENCES:
patent: 4957808 (1990-09-01), Arai et al.

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