JPH0365280B2 - - Google Patents

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 bonded to a porous support. More specifically, the present invention relates to a base paper for thermal stencil printing that can be subjected to a method of perforating with a thermal head, rather than the conventional perforation method of perforating the image area by absorbing heat rays from a halogen lamp or a xenon lamp. [Conventional Method] Stencil printing base papers that can be perforated by infrared irradiation have been 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, the special public official court in 1977-
Publication No. 7623 describes the use of propylene, polyamide, polyethylene, vinyl chloride-vinylidene chloride copolymer, and Japanese Patent Publication No. 1184-1984 discloses the use of propylene, ethylene, butene-1, isoprene, tetramethylbutadiene, and vinyl chloride. Japanese Patent Publication No. 52-4969 describes the use of a vinyl-based synthetic resin film. However, when stencil printing base paper is made using these synthetic resin films and then perforated with a thermal head for a thermal printer or thermal facsimile, there are almost no perforations, and the desired plate making for thermal stencil printing is not possible. The problem is that it cannot be obtained. In the case of infrared irradiation (tungsten halogen lamp, 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 at most 1 mj/dot, so the thickness of the film This is thought to be due to the difference in heat capacity caused by the Furthermore, when using conventional infrared irradiation for perforation, most of the synthetic resin films mentioned above can be easily perforated up to a thickness of about 15μ, but when using a perforation method using a thermal head, the perforation rate is extremely poor for thick films. As a result, ink flow through mimeograph printing is poor, and as a result, the image density becomes low, resulting in a problem that only discontinuous images with broken line drawings are obtained. In addition, base paper for heat-sensitive stencil printing is generally made by laminating a thermoplastic synthetic resin film and a porous support (tengu paper, rayon-mixed Japanese paper, non-woven fabric, screen, etc.) with an adhesive resin, but synthetic When a resin film or support material expands or contracts due to heat, it curls in one direction due to the bimetallic principle, which is a problem. In particular, stretched synthetic resin films tend to curl toward the film surface due to shrinkage due to temperature, aging, etc. It has been difficult to obtain a plate for heat-sensitive stencil printing using a thermal head. Also, JP-A-57-182495 and JP-A-51-
Publication No. 2513 discloses a base paper for thermal stencil printing in which a film made of polyethylene terephthalate is laminated onto a support, but since these base papers are made so that they can be perforated by infrared irradiation, thermal heads cannot be used. When holes are made using this method, there are drawbacks such as the film being fused to the thermal head and the drilling residue adhering to the thermal head. [Objectives] The present invention has been made in view of the above-mentioned current situation, and its objects are to increase the film porosity and improve the printing image quality in thermal head perforation, to prevent curling of stencil paper, and to fuse the film to the thermal head. Another object of the present invention is to provide an industrially excellent base paper for heat-sensitive stencil printing, which makes it possible to reduce the amount of perforation residue attached. [Structure] According to the findings of the present inventors, in perforation of stencil printing paper using a thermal head, the heat capacity of the film, in addition to the melting point of the synthetic resin film, controls the degree of perforation (porosity). was discovered. In other words, the heat capacity of the film is related to the thickness of the film, and the thinner the film, the better the holes will be. However, most films other than polyester have a thickness of 10 microns or more, and the thinnest film produced industrially currently has a thickness of 4 to 6 microns. Films with a thickness of 4μ or more have a very poor porosity even if their melting point is low. It has also been found 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 and used as a base paper for stencil printing, 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 greater the amount of debris attached. 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, perforation will not occur unless the melting point of the film is lower than the temperature of the thermal head. Furthermore, if no anti-stick layer is present on the polyester film, the thermal head and the polyester film will become more fused and the amount of perforation residue will increase. The present invention has been made based on these findings. That is, according to the present invention, a polyester film having a thickness of 1 to 3 μm is laminated to a porous support,
Furthermore, there is provided a base paper for thermal stencil printing characterized in that a stick prevention layer is provided thereon so that it can be perforated by a thermal head. The first feature of the present invention is that a base paper made by laminating a porous support and a polyester film is used as a base paper for thermal stencil printing, and the thickness of the polyester film is limited to a range of 1 to 3 μm. As is clear from the above findings, the main reason for limiting the thickness of the polyester film to the above range is to improve the printed image by increasing the porosity of the film during thermal head perforation. If the thickness of the polyester film is less than 1μ, bonding becomes difficult, and if the thickness of the polyester film exceeds 3μ, excessive energy is required for drilling, which significantly shortens the life of the thermal head. The purpose of the period is not achieved. A second feature of the present invention is that a sticking prevention layer is provided on the laminated polyester film to prevent sticking with the thermal head. If such a stick prevention layer is not provided, the polyester film will fuse to the thermal head and the intended purpose of the present invention will not be achieved. The thickness of the anti-stick layer is suitably 0.01 to 1.0 microns. When the film thickness of the stick prevention layer is less than 0.01μ,
Stitching occurs, which not only makes it impossible to obtain a clear printed image, but also makes it difficult to convey the base paper.
Moreover, if the film thickness exceeds 1.0 μm, it is undesirable because more residue adheres to the thermal head, resulting in uneven drilling. As the material for forming the sticking prevention layer, any material can be used as long as it can suppress sticking, such as a fluorine-based compound. Porous supports used in the present invention include 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 (eg, thermal bonding). Any known thermal head can be used, such as thermal heads for line printers that print using thermal paper or thermal transfer ribbon, and thermal heads for serial printers that print with facsimile. Examples include those used in the printing parts of word processors, label printers, CAD, etc. In addition, the current application time by the thermal head is 3ms.
It is preferably within 2 ms, preferably within 2 ms. If the energization time exceeds 3 ms, not only will the plate making time become longer, but the perforation properties will deteriorate and the sticking with the thermal head will increase. [Example] The present invention will be further explained with reference to Examples below, but the present invention is not limited thereto. [Reference Example] A thin film was selected from various stretched thermoplastic synthetic resin films currently available on the market, and a base paper for stencil printing was prepared according to the following procedure. Type of film used Film thickness (μ) No. 1 Vinylidene chloride 10 2 Vinyl chloride (hard) 15 3 (soft) 15 4 Vinyl chloride-vinylidene chloride copolymer 6 5 Polypropylene 9 6 〃 4 7 Nylon 6 15 8 Polystyrene 30 9 Polyethylene (low pressure) 15 10 Polyacrylonitrile 10 11 Polyester 6 12 〃 4 13 〃 2 Vinyl acetate-based adhesive is applied to the above various films using a wire bar, and porous thin paper with a thickness of 4 μ is applied. (Tengucho) were stacked and laminated together using wet lamination to produce a base paper for stencil printing. A thermal head (Ricoh thermal fax machine) is attached to the stencil printing base paper produced as described above.
Documents are read by RIFAX5320H, thermal head is used to write and perforate, head energy is fixed at 1.0mJ/dot), a thermal stencil is created, and this is used to print on a mimeograph machine (Ricoh Hi Printer E-80). The applicability of the film was evaluated. The results are shown in Table 1 below.

【table】

[Table] *Evaluation by microscopic observation From the above results, it is clear that even if the melting point of the film is low, if the film is thick, the perforation performance will be inferior when the film is opened using a thermal head. . This is considered to be due to the heat capacity caused by the difference in thickness. Example 1 Six types of polyesters having different thicknesses were laminated using a vinyl acetate adhesive (2 g/m ² ) on a 40 μm thick porous support made of Tengujo paper. In order to prevent sticking with the thermal head, a 2% aqueous solution of a fluorine-based compound (Daifree MS810 (manufactured by Daikin Industries)) is applied to the surface of the laminated film to form an overcoat layer with a thickness of 0.1 μm. A base paper for stencil printing was prepared.

【table】

[Table] Next, we investigated the relationship between the energy applied to the thermal head, the pore opening state (photo observation), and the print quality by varying the applied voltage (power) and energization time for these samples, and the results are shown in Table 2 below. The results were obtained.

【table】

[Table] Example 2 Samples G to L were prepared by changing the thickness of the overcoat layer of Sample D in Example 1 as shown below, and the presence or absence of stitching after continuous plate making of 20 plates was examined in the same manner as Example 1. . The results are shown in Table 3. Regarding the adhesion of waste, the state of adhesion of waste on the thermal head after continuous plate making of 200 sheets at 3.0 ms and 0.6 mJ was investigated. Sample No. Thickness of overcoat layer (μ) ^** G 0 H 0.01 I 0.1 K 1.0 *Comparative example

【table】

〔effect〕

The heat-sensitive stencil printing base paper of the present invention constructed as described above has the following effects. Since the film is perforated evenly and continuously, when mimeograph printing is performed, a continuous line drawing with excellent ink alignment can be obtained, and the image density in the solid image area is also high, resulting in excellent quality printing. give an image. Since sticking and residue adhesion of the thermal head can be reduced, transportability during plate making is improved and dimensional reproducibility is improved. To prevent stencil paper from curling over time during the production of a plate for heat-sensitive stencil printing. The stencil paper has high lamination strength (unlike polyolefin films, it can be wet laminated or dry laminated without corona discharge treatment), and exhibits excellent durability.

Claims (1)

[Claims] 1. A base paper for heat-sensitive stencil printing, characterized in that a polyester film having a thickness of 1 to 3 μm is laminated to a porous support, and a stick prevention layer is further provided thereon, so that it can be perforated by a thermal head.