JPS6048398A - Thermal screen printing stencil paper - Google Patents

Abstract

PURPOSE:To attain to enhance film porosity in the perforation of a thermal head and printing quality while preventing the curling of a screen printing stencil paper, by using a polyester having a specific thickness or less as a thermoplastic synthetic resin film. CONSTITUTION:A polyester film having a thickness of 4mum or less, pref., 1-3mum is laminated to a porous support such as porous Indian paper or porous synthetic fiber paper, if necessary, by using an adhesive to obtain the objctive screen printing stencil paper. Furthermore, according to necessity, an overcoat layer comprising a fluorine contained resin may be further provided to the surface of the film after lamination. EFFECT:The fusion bonding of the film and the adhesion amount of perforation dregs to a thermal head are reduced. Even if no corona discharge treatment is performed, wet or dry lamination is enabled.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a base paper for heat-sensitive stencil printing in which a polyester film is laminated to a porous support. More specifically, the present invention relates to a thermal stencil printing base paper which is used for a method of perforating with a thermal head, rather than a conventional perforation method of perforating the image area by absorbing heat rays from a halogen lamp or a xenon lamp. .

BACKGROUND OF THE INVENTION Conventionally, stencil printing paper which can be perforated by infrared irradiation is known. A typical example is a thermoplastic synthetic resin film and porous thin paper bonded together using an adhesive. Furthermore, various synthetic resin films that can be perforated by infrared irradiation have been proposed. For example, Japanese Patent Publication No. 41-7623 describes the use of propylene, polyamide, polyethylene, vinyl chloride-vinylidene chloride copolymer, and Japanese Patent Publication No. 47-1184 discloses the use of propylene, ethylene, butene-1, imprene, and tetrapropylene. It is possible to use a copolymer of methylbutadiene and one selected from vinyl chloride and
Publication No. 69 describes the use of a vinyl-based synthetic resin film. However, when stencil paper is prepared using these synthetic resin films and perforations are performed using a thermal head for a thermal printer or thermal facsimile, there is a problem that the perforations are almost never made. This U infrared a irradiation (tungsten halogen lamp,
In the case of a xenon lamp, the image area of the film receives a large amount of thermal energy, but in the case of a thermal head, the thermal energy is approximately 1 mJ/dot at most.
This is thought to be due to the difference in heat capacity caused by the thickness of the film.

Furthermore, when using the conventional perforation method using infrared irradiation, most of the synthetic resin films can be perforated up to a thickness of about 15 μm, but when using the perforation method using a thermal head, the perforation rate becomes extremely poor for thick films. Therefore, there is a problem in that ink penetration by mimeograph printing is poor and the image density is low, resulting in only discontinuous images with broken line drawings. In the case of heat-sensitive stencil paper, a thermoplastic synthetic resin film and a porous support (tengucho paper, rayon-mixed washi paper,
Non-woven fabrics, screens, etc.) are generally bonded together using adhesives and resins. In this case, there is a problem in that when the synthetic resin film or support expands and contracts due to heat, it curls in one direction due to the bimetallic principle.

In particular, a stretched synthetic resin film shrinks due to temperature, time, etc., and thus curls toward the film surface. Therefore, it is desired to develop a stencil printing paper suitable for perforation by a thermal head.

Purpose The present invention was made in view of the above-mentioned current situation, and its purpose is to increase the film porosity in thermal head perforation, improve printing image quality, prevent stencil paper from curling, fuse the film to the thermal head, and perforate the film. This includes reducing the amount of residue M.

Structure The present invention is based on the findings obtained from the results of studies on the applicability of various synthetic resin films that can be perforated by infrared irradiation to thermal head perforation. That is, the present invention provides thermoplastic synthetic 4rI (
It is characterized in that a polyester film with a thickness of 4 μm or less is used as the fat film.

According to the above findings, it has been found that in perforation of stencil paper by a thermal head, the degree of perforation (porosity) is controlled not only by the melting point of the synthetic resin film but also by the heat capacity of the film. In other words, the heat capacity M of the film is related to the thickness of the film, and the thinner the film, the more holes are formed. However, the current situation is that most films other than polyester have a thickness of 10 microns or more, and even the thinnest film produced industrially has a thickness of 4 to 6 microns. A film with a thickness of 4 μm or more has a very poor opening rate even if the melting point is low. It was also discovered that films other than polyester are easily affected by temperature and humidity and have large expansion and contraction. Therefore, when laminated with a porous support to form a stencil paper, curling is large due to temperature, humidity and aging. Furthermore, it has been found that the lower the melting point of the film and the thicker the film, the greater the degree of fusion with the thermal head, and that the thicker the film, the more debris adheres to the film. Therefore, when perforating a film by applying a certain amount of energy (temperature) to the thermal head, the higher the melting point of the film and the thinner the film, the more advantageous it is to prevent these phenomena. However, the melting point of the film must be lower than the temperature of the thermal head to be perforated.

As mentioned above, the present invention has been made based on various findings, and it applies a thermal stencil printing base paper made by laminating a thermoplastic synthetic resin film and a porous support to perforation using a thermal head. Therefore, a polyester film having a thickness of 4 microns or less, preferably 1 to 3 microns, is used as the synthetic resin film. As is clear from the above findings, the main reason for limiting the thickness of the polyester film to 4 μm or less is to increase the film porosity under the thermal head perforation pressure and improve the print image quality.

As the porous support used in the present invention, porous thin paper (tengucho), porous synthetic fiber paper, various woven fabrics, non-woven fabrics, etc. can be used. Further, the porous support and the polyester film can be bonded together with or without using an adhesive (for example, by thermal bonding). Also,
In order to prevent fusion (sticking) with the thermal head, an overcoat layer of fluorine resin or the like may be provided on the surface of the laminated film.

EXAMPLES The present invention will be further explained with reference to Examples below, but the present invention is not limited thereto.

Example 1 A thin film was selected from various stretched thermoplastic synthetic resin films currently on the market, and a stencil printing base paper was prepared according to the following procedure.

Flat 1 Vinylidene chloride 10 2 Vinyl chloride (hard) 15 3 (soft) 15 5 Polypropylene 9 6 l 4 7 Nylon 6 15 8 Polystyrene 30 9 Polyethylene (low pressure) 15 10 Polyacrylonitrile 10 11 Polyester 6 12 I 4 13 〃 2 Above Vinyl acetate-based adhesive is applied to various types of films using a wire paper, and porous thin paper (tengucho) f! :Laminated by layered wet lamination,
A stencil paper was made.

A thermal head (
Document reading and thermal head writing and punching using the Recosamar facsimile RIFAX5320H, head energy 1. A thermal stencil was made by making 9 holes using OmJ/dot fixation) and printed using a mimeograph machine (Ricoh High Printer E-80) to evaluate the applicability of various films. The results are shown in Table 1 below.

From the above results, it is clear that even if the film has a low melting point, if the film is thick, the hole-opening performance is poor when the holes are formed using a thermal head. This is thought to be due to thermal expansion caused by the difference in thickness.

Example 2 Five types of polyesters having different thicknesses were laminated onto a 40 μm thick porous support made of Tengucho paper using a vinyl acetate adhesive (2 g/rn2). In order to completely prevent sliding with the thermal head, the surface of the laminated film was overcoated with a fluorine-based resin having a heat resistance temperature of 480° C., thereby producing a complete base paper for stencil printing.

Sample shop Film thickness (μ) 11.5 2 36.0 45.5 4 Next, for these samples, the applied voltage (power) and energization time of the thermal head were varied to determine the energy and pore opening state (photo). When we investigated the relationship between (observation) and print image quality, we obtained the following results. Table 2 shows the energizing time of 3.
Table 3 shows the results when the current was set to 0m8.
The results are shown when the time is set to 2.0 ms.

Table 2 Table 3 0 Consecutive holes are well formed and the print quality is good.

Δ The line drawings in the printed image are discontinuously apertured and can be identified as discontinuous lines like dotted lines.

× The holes are not opened at all and ink cannot pass through.

From the above results, it can be seen that the perforation state of the stencil paper changes depending on the thickness of the film and the energy of the thermal head. However, if you actually give the same energy (
(Energy - Power × Time) It is better to open holes by increasing the power (voltage) than by increasing the energization time.The output of the thermal head is also limited in relation to the head life (currently I''j, maximum (approximately 1.5 mJ/dot).Despite the above results, all the desired effects of the present invention can be achieved with a polyester film having a thickness of 4 μm or less.

Effects The heat-sensitive stencil printing base paper of the present invention constructed as described above has the following effects.

■ The holes in the film are evenly and consecutively perforated, so when mimeographed, the ink passes through easily and the line drawings are continuous. Further, the image density of the solid image portion is also high, and the image quality is improved.

■ 15g of curling due to aging of the stencil paper does not occur.

■ Lamination requirement is high (<sq+) Unlike off-air film, wet lamination or dry lamination is possible without corona discharge treatment etc.)
.

Patent applicant Rico Co., Ltd.

Claims (1)

[Claims] A base paper for thermal stencil printing, characterized in that a polyester film having a thickness of 4 μm or less is laminated to a porous support and can be perforated with a thermal head.