GB2176621A

GB2176621A - Heat-sensitive stencil paper

Info

Publication number: GB2176621A
Application number: GB08600015A
Authority: GB
Inventors: Yoshiaki Hori; Kazutsugu Hayashi
Original assignee: Asia Stencil Paper Co Ltd
Current assignee: Asia Stencil Paper Co Ltd
Priority date: 1985-06-21
Filing date: 1986-01-02
Publication date: 1986-12-31
Also published as: GB2176621B; JPH0334476B2; GB8600015D0; JPS61293899A

Abstract

Heat-sensitive stencil paper comprising a porous supporting sheet and a sheet of polyvinylidene fluoride film bonded thereto can be successfully perforated with a thermal head provided on for example a thermal printer.

Description

SPECIFICATION Heat-sensitive stencil paper This invention relates to heat-sensitive stencil paper that can be perforated with a thermal head, provided on a thermal printer or the like, for the manufacture of stencils to be used for printing.

Stencil paper of this type is generally composed of a porous supporting sheet and a sheet of thermoplastic synthetic resin film bonded thereto, polyester, polyvinyl chloride, vinyl chloride/vinylidene chloride copolymer, polyethylene or polypropylene being commonly used as the thermoplastic resin. When a film made of any one of the above-mentioned polymers is perforated by means of a thermal head provided on a thermal printer a thermal facsimile molten thermoplastic resin film tends to stick to the thermal head. If this happens, noise due to the movement of thermal head becomes louder and the movement of thermal head is obstructed, resulting in irregular perforation, damage to the stencil paper, or to other related troubles.Formation of a protective layer on the surface of the thermoplastic resin film has been proposed as a means of preventing such sticking of resin melts to the thermal head. However this method suffer from the problem that molten protective layer adheres to the thermal head, thereby badly affecting it perforating performance.

When conventional heat-sensitive stencil paper, made of polyester, polyvinyl chloride or other commonly used thermoplastic resin, is processed using a thermal head, perforation itself is confined only within the area that corresponds to the effective area on each tip because of the minute amount of energy generated there, making it difficult to produce stencils with sharp images. More particularly, when conventional heat-sensitive stencil paper is perforated using a thermal head and used for printing on a rotary mimeograph, the printed characters look so rough and coarse that one can recognise at a glance that each is an aggregation of many dots.On the other hand, printed characters obtained by a genuine printing means (for example, by means of a heat-transfer type carbon ribbon or a heat-sensitive luminous paper) are very sharp and clear, and one can hardly discern that each character is made up of many dots. This is probably because the portion of heat-transfer type carbon ribbon made molten by the heat energy generated at each thermal head tip and transferred to the printing paper occupies an area larger than the effective area of each tip, or because the area of printing paper coloured by the heat energy generated at each thermal head tip is larger than the effective area of each tip.

According to the present invention, there is provided a heat-sensitive stencil paper for perforation by means of the thermal head tips of a thermal printer, which comprises a sheet of polyvinylidene fluoride film with a thickness not less than 2jt and not more than 98 bonded to a porous supporting sheet capable of absorbing polyvinylidene fluoride film melt.

Heat-sensitive stencil paper according to this invention is free from the problem of molten film material sticking to the thermal head and gives perforations sufficiently larger than the effective area on each tip of the thermal head, thereby achieving sharp and clear prints. The heat-sensitive paper does not need protective layer which would be a problem in itself in fusing onto the thermal head.

A stencil paper embodying this invention utilises a thin paper capable of absorbing polyvinylidene fluoride melt as the porous supporting sheet. Typical examples of this thin paper are materials made of fibres of less than 3 deniers, for example, synthetic fibres, such as polyester, polyvinyl alcohol and polyamide, e.g. nylon, and natural fibres, such as hemp, pulp, and fibre of Broussonetia kazinoki and Edgeworthia papyrifera. These fibres may be used either as sole fibres or in combination.A suitable weight for the thin paper is in the range from 6 to 14 g/m2, more preferably in the range from 8 to 12 g//m2, while its thickness is preferably in the range from 20 to 60 ,u, more preferably in the range from 25 to 50 The polyvinylidene fluoride film used is preferably biaxially oriented with its draw ratio, although depending on film thickness, preferably lying in the range from 100 to 300% in both the longitudinal and transverse directions.

Sufficient perforation by the thermal head tips cannot be expected if the thickness of the polyvinylidene fluoride film exceeds 9 , because the heat energy generated in an ordinary thermal head in only about 2 millijoule per tip. If the thickness is less than 2 ,lt, on the other hand, perforations excessively larger than the effective area on each tip will be formed, making the resulting printed characters indistinct. Therefore the thickness of polyvinylidene fluoride film used in the heat-sensitive stencil paper of this invention should be in the range from 2 to 9 ,u.

When heat-sensitive stencil paper according to this invention is perforated on a thermal printer or the like, the molten polyvinylidene fluoride film is absorbed by the porous base material without sticking to the thermal head.

Therefore there is no need for a protective layer on the heat-sensitive paper. In addition, perforations thus prepared are moderately larger than the effective area on each tip of thermal printer. Sharp and clear printing can thus be achieved by using the stencil obtained above.

The following examples, in which reference is made to the accompanying drawing, illustrate this invention.

EXAMPLE 1 A sheet 2 of polyvinylidene fluoride film 6,u thick and a porous supporting sheet 1, made of polyester fibre and 12 g/m2 in weight, were bonded together with the aid of a layer 5 of acrylic adhesive, as shown in the accompanying drawing. The adhesive layer 5 was coated on the surface of the polyvinylidene fluoride film 2 in an amount of 1.5 g/m2 by using a gravure coater (adhesive applicator), and was dried by hot air.

The heat-sensitive stencil paper thus prepared was utilised in the printer of a desk-top word processor (Silver Seiko Ltd; Model JX20) the printer being provided with a thermal head 3 by means of which the polyvinylidene fluoride film was perforated to form minute openings for transmission of printing ink. The melts produced by the film were fully absorbed by the porous supporting sheet and did not stick to the thermal head 3, and stencil preparation was completed without any trouble. Even when two sheets of heat-sensitive stencil paper were prepared in turn by following this procedure, no sticking of the thermal head occurred, and no decline in perforating performance of the thermal head was observed. The stencil paper thus prepared was used for printing on a rotary mimeograph (Gestetner Limited; Model 4170).The prints thus obtained did not compare unfavourably in quality with those obtained by direct printing on a thermal printer.

EXAMPLE 2 (Comparative) Heat-sensitive stencil paper was prepared by the same method as in the foregoing example, except that a sheet of polyester film 3y thick was used in place of the polyvinylidene fluoride film. When the stencil paper thus prepared was perforated in the same manner as above, the molten film tended to stick to the thermal head, and, as a consequence, a part of the film itself became fused to the thermal head, resulting in film breakage. When printing on the rotary mimeograph was performed in the same way as in the foregoing example, coarse characters were obtained even in areas corresponding to normal perforations. These characters were so coarse that one could easily recognise that each character was made up of many dots, and it was impossible to obtain prints comparable in sharpness with those obtained by direct printing on a thermal printer.

Claims

1. A heat-sensitive stencil paper for perforation by means of the thermal head tips of a thermal printer, which comprises a sheet of polyvinylidene fluoride film with a thickness not less than 2y and not more than 98 bonded to a porous supporting sheet capable of absorbing polyvinylidene fluoride film melt.

2. A heat-sensitive stencil paper as claimed in claim 1, wherein the porous supporting sheet is a paper made of a synthetic fibre.

3. A heat-sensitive stencil paper as claimed in claim 2, wherein the porous supporting sheet is a paper made of polyester, polyvinyl alcohol or polyamide fibre.

4. A heat-sensitive stencil paper as claimed in any preceding claim, wherein the porous supporting sheet is made of fibre of less than 3 denier.

5. A heat-sensitive stencil paper as claimed in any preceding claim, wherein the porous supporting sheet has a weight of 6 to 14 9/m2.

6. A heat-sensitive stencil paper as claimed in any preceding claim, wherein the porous supporting sheet has a thickness of 20 to 60 1.

7. A heat-sensitive stencil paper as claimed in any preceding claim, wherein the polyvinylidene fluoride film is biaxially oriented.

8. A heat-sensitive stencil paper as claimed in claim 7, wherein the draw ratio of the polyvinylidene fluoride film is from 100 to 300% in both the longitudinal and transverse directions.

9. A heat-sensitive stencil paper, substantially as described in the foregoing Example 1.