JPH04221698A - Improved tissue paper for thermal stencil paper - Google Patents

Abstract

PURPOSE:To enhance the image properties of printed matter to a large extent by rationalizing the void volume of tissue paper for heat sensitive stencil paper used in a full-automatic digital screen printing machine. CONSTITUTION:A fiber having a mean fiber diameter of 3.5-12.0mu finer than a general-purpose natural, synthetic or regenerated fiber and pref. fiber length of 2-5mm is well dispersed in water alone or together with the general-purpose fiber and subjected to a papermaking process to obtain tissue paper properly small in void volume and mean opening area and reduced in the irregularity of an opening area and having good ink passing properties (high image properties).

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to thin paper for heat-sensitive stencil paper. More specifically, the present invention relates to a thin paper used as a porous support for a base paper for thermal stencil printing, which is subjected to perforation making by receiving heat from a thermal head, a xenon flash lamp, or the like.

0002

[Prior Art] The porous thin paper used for heat-sensitive stencil paper includes (1) so-called Japanese paper made from natural fibers such as Kozo, Mitsumata, Manila hemp, etc.
3), (2) Paper made from recycled fibers and synthetic fibers such as rayon, vinylon, polyester, and nylon, (3) Natural fibers mentioned in (1) above and recycled fibers and synthetic fibers mentioned in (2) above. Mixed paper made by mixing
(Japanese Patent Publication No. 18728), (4) So-called polyester paper obtained by heat-pressing a thin paper made by mixing polyester fibers and undrawn polyester fibers as binder fibers using hot rolls (Japanese Patent Publication No. 1988-8809) etc. are generally known.

[0003] Since such thin paper has the problem of deterioration in function due to deformation or dimensional change due to humidity or temperature, a proposal has been made to reduce dimensional change when wet (Japanese Patent Application Laid-Open No. 61-254396). In addition, a proposal was made for a process in which thin paper is impregnated with a synthetic resin liquid and can also function as an adhesive between the thin paper and film (Special Publication No. 55-47).
997), and a proposal for high-quality thin paper obtained by combining a specific range of polyester fibers and a specific resin within a limited range (JP-A-1-271293).
etc. are being done. Furthermore, regarding polyester paper, we proposed a detailed manufacturing method for making it superior in dimensional stability and heat resistance (Japanese Unexamined Patent Publication No. 58-76597).
(Japanese Patent Application Laid-Open No. 58-76598), a proposal for improvement by fine denier (Japanese Patent Publication No. 62-55999), a proposal for improving rigidity (Japanese Patent Application Laid-Open No. 2-67197)
etc. are being done. In addition, in the digital perforation method, a proposal was made to improve image quality by specifying the pore area, average pore area, etc.
No. 0593) has been made. However, high image quality (good ink permeability, character resolution, A film that satisfies the following requirements (excellent image quality, uniform solid areas, and few white spots) has not yet been obtained.

0004

[Problems to be Solved by the Invention] Thin paper according to the prior art has the following drawbacks. In other words, because the aperture area is large and the variation is large, the ink passage is uneven, and where too much ink comes out, there is set-off (ink gets on the back of stacked printed materials), and no ink comes out. A clear image cannot be obtained because the area becomes white or blurred. Japanese Patent Application Laid-Open No. 61-53092 stipulating the porosity of thin paper
In the case of the publication, it is effective for the perforation of the film, but
It is insufficient in terms of ink permeability. Furthermore, JP-A-2
In the case of Publication No. 30593, the porosity, average pore area, and compression work are specified, but the average pore area is too large, so it is not satisfactory in terms of ink permeability.

[0005] As a result of extensive research in order to improve the above-mentioned drawbacks of thin paper used for thermal stencil paper, the present inventor has found that by using fibers with a small average diameter, the pore area can be made small and the variation can be reduced. It has been found that good image quality can be obtained.

[0006]

[Means for Solving the Problems] The present invention has an average pore area of 600 to 1,400 μ2 and a standard deviation of the pore area of 1.8 μm.
This thin paper for heat-sensitive stencil paper is characterized by having a porosity of 15 to 40% of 00 μ2 or less. In the present invention, the paper-made thin paper has a basis weight of 5 to 15 g/m2 and a thickness of 10 to 5 g/m2.
Preferably, it is 0μ. More preferably, the basis weight is 8~
13g/m2, thickness 25-40μ, and density 0.25-0.45g/cm3. In order to uniformly extrude the ink from the pores of the film within the preferred basis weight and thickness range, the preferred length (preferably 2 to 5
It is necessary to increase the number of fibers by using thin fibers (mm) and uniformly disperse the fibers to appropriately divide the voids in the thin paper and to make them as uniform as possible. Specifically, the average pore area is 600 to 1,400 μ2, the standard deviation of the pore area is 1,800 μ2 or less, and the pore size is 15 to 15.
40%, preferably an average pore area of 700 to 1,
200μ2, the standard deviation of the open pore area is 1,200μ2 or less, and the open area ratio is 18 to 30%.

[0007] If the average aperture area is larger than 1,400 μ2, the ink will come out unevenly, resulting in missing parts and unclear parts of the image. On the other hand, if it is smaller than 600 μ2, poor dispersion of fibers will occur and white spots will occur due to fiber flocking. Furthermore, if the aperture ratio exceeds 40%, the ink will come out too locally, which is undesirable because, when viewed as a whole, the dots of the characters will be poorly connected and the resolution will be poor, and white spots will occur in solid areas. If the aperture ratio is lower than 15%, the ink permeability will be poor, the dots of characters will be poorly connected, the resolution will be poor, and white spots will easily occur in solid areas, which is not preferable. Note that the pores of the porous thin paper in the present invention are portions through which light passes and appear to form pores, and are a two-dimensional analysis of the pores through which ink passes.

[0008] The fibers constituting the thin paper of the present invention are as follows:
Any of natural fibers, recycled fibers, and synthetic fibers may be used, but preferred are bast fibers such as Manila hemp and flax, recycled fibers such as viscose rayon fibers, cuprammonium rayon fibers, and synthetic fibers such as nylon, polyester, and vinylon. It is. These fibers may be made individually or mixed, but at least one type needs to be fine.

[0009] The thin paper according to the present invention is produced by a commonly used method. At this time, the dispersant used, a sticky agent (preferably polyethylene oxide or polyacrylamide), an antifoaming agent, a mold release agent, an antistatic agent, a paper strength enhancer during paper making, a sizing agent, etc. may be mixed. Needless to say. When natural fibers and synthetic fibers are mixed in the present invention, so-called binder fibers can be used as the binder, but this is not preferred because the fiber diameter is large and deteriorates image quality. Binding using a coated material is preferred. Coated materials include viscose, polyvinyl acetate resin, acrylic resin, vinyl chloride resin, SBR
, synthetic rubbers such as NBR, urethane resins, epoxy resins, etc., which can be used in either solvent solution type or emulsion type, and are preferably urethane resins with strong binding strength and less film tension (does not impede image quality). It is an epoxy resin.

0010

[Example 1] The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited to these Examples. % in Examples and Comparative Examples represents % by weight. The characteristics were measured and evaluated using the following methods. (1) Pore analysis (average pore area, standard deviation of pore area, pore ratio) A 37x enlarged copy was created using a Canon enlarger, and a high-definition image analysis file system was created for an area of 8 cm x 8 cm. (Asahi Kasei Industries, Ltd.) was used for analysis. (2) Evaluation of image quality 1) Printing unevenness Amorphous copolyester film (superior to crystalline polyester film in terms of plate-making sensitivity) as a thermosensitive film (stretched thermoplastic synthetic resin film) and the present invention Thin paper as a porous support is laminated with a wet laminator using a wet laminating adhesive (a solution in which an epoxy compound and a polyamine resin are dissolved in a weight ratio of 17:83 using isopropyl alcohol as a solvent). A heat-sensitive stencil paper (hereinafter referred to as master) was used. Using this master, a thermal head with a heating element density of 400 dots/inch (manufactured by Toshiba Corporation, TPH256R8D) was attached to a thermal head test printing device (manufactured by Okura Electric Co., Ltd., thermal coloring device TH-PMD).
) is equipped with a fully automatic digital stencil printing machine (Riso Kagaku Manufactured by Kogyo Co., Ltd., RC1
15). The printed matter was evaluated visually. ○ indicates that there are no uneven thickness of letters or thin lines or white spots in solid black areas, × indicates that letters or thin lines have partial breaks or uneven thickness, or noticeable white spots in solid black areas, △ It is considered to be somewhere between ○ and ×, and is at a level that can be used practically.

2) Gradation Using the printing device described above, the dot density was changed and plate making was performed under conditions that produced images with gradation, and the prints printed with the printing machine described above were evaluated by visual judgment. went. ○ indicates that each dot is well reproduced, × indicates that the dots are noticeably missing, and △ indicates that the dots are intermediate between ○ and × and are at a level that can be used practically. (3) Basis Weight The mass of 10 test pieces (31.5 cm x 31.5 cm) that had been left to stand for 24 hours at constant temperature (22° C.) and constant humidity (66% relative humidity) was measured. (4) Thickness Measured according to JISP-8118

0012

[Examples 1 to 3] (A) Manila hemp (raw hemp) was digested with alkali, washed, diluted with water to a concentration of 3%, and beaten with a beater to a freeness of 18°SR (JISP-8121). Manila hemp was uniformly mixed with the synthetic fibers shown in Table 1 (display names and properties of each listed) with the composition shown in Table 2, and an aqueous solution of epoxidized polyamide resin was added to the mixture to give a ratio of 2% to the fibers. The mixture was added and mixed uniformly. This was used as paper stock to make thin paper using a circular wire paper machine. Tissue paper has a drying temperature of 1
It was dried using a Yankee dryer at 30° C. and rolled up. (B) Each thin paper obtained in (A) above was coated with urethane resin (aqueous emulsion: Daiichi Kogyo Seiyaku Co., Ltd., Superflex 100) using a gravure coating machine. The coating amount was 1.0 g/m2. (C) The basic characteristics and characteristics (imageability) of the resin-treated thin paper obtained in (B) above were evaluated, and the results shown in Tables 3 and 4 were obtained, respectively.

[0013]

[Example 4] Freeness 25°SR (JISP-18
21) 30% sisal, 20% polyester fiber [labeled name PET (C)], and 20% vinylon fiber [labeled name Vinylon] were mixed uniformly, and then (A
Tissue paper was made in the same manner as in section ), and a roll was obtained. The resin processing of this product and the evaluation of the basic characteristics and characteristics (image quality) of the resin-processed thin paper were both carried out in Example 1.
It was carried out in the same manner as in sections (B) and (C) of ~3. The results are shown in Tables 3 and 4.

[0014]

[Comparative Example 1] Manila hemp and polyester fiber [display name PET (D)] used in Examples 1 to 3 were mixed uniformly in the composition shown in Table 2, and then Tissue paper was made in the same manner as above, and a roll was obtained. Evaluations of the resin processing of this product and the basic characteristics and characteristics (image quality) of the resin-processed thin paper were performed in Examples 1 to 3 (B
), carried out in the same manner as in section (C). The results are shown in Tables 3 and 4.

[0015]

[Comparative Example 2] The thin paper made of 100% Manila hemp used in Examples 1 to 3 was made in the same manner as in Section (A) of Examples 1 to 3,
Got that take-up roll. The resin processing of this product and the evaluation of the basic characteristics and characteristics (imageability) of the resin-processed thin paper were performed in the same manner as in sections (B) and (C) of Examples 1 to 3. The results are shown in Tables 3 and 4.

[0016]

[Comparative Example 3] The thin paper made of 100% sisal used in Example 4 was produced in the same manner as in Examples 1 to 3, and a roll was obtained. The resin processing of this product and the evaluation of the basic characteristics and characteristics (imageability) of the resin-processed thin paper were performed in the same manner as in sections (B) and (C) of Examples 1 to 3. The results are shown in Tables 3 and 4.

[0017]

[Table 1]

[0018]

[Table 2]

[0019]

[Table 3]

[0020]

[Table 4]

[0021]

[Effects of the Invention] The present invention is a thin paper for heat-sensitive stencil paper having apertures in a specific range, and can obtain the following excellent effects. (1) Fibers are uniformly dispersed and have good texture. (2) The perforation of the film and the permeability of ink are good, and the image when printed is clear. (3) Ink does not come out too much locally and there is little set-off.

[0022] In this way, it is possible to have excellent performance as a porous support.

Claims (1)

[Claims] [Claim 1] Average pore area 600 to 1,400 μ2
, a standard deviation of pore area of 1,800 μ2 or less, and a porosity of 15 to 40%.