JPH05345489A - Improved tissue paper for thermal stencil paper - Google Patents

Abstract

PURPOSE:To enhance image properties, in the title tissue paper as a porous support used in a thermal head, by specifying an average aperture area, the standard deviation of an aperture area and an aperture ratio. CONSTITUTION:A fiber with an average fiber diameter of about 2-12.0mum and a length of about 2-5mm finer than a general-purpose natural fiber, a synthetic fiber and a regenerated fiber, pref., a regenerated fiber of Manila hemp is dispersed in water independently or dispersed in water to be mixed with a general-purpose fiber to form tissue paper with a basis wt. of about 5-15g/m<2>, a thickness of about 10-50mum and a density of about 0.25-0.45g/cm<3> by a papermaking process. The average aperture area of this tissue paper is set to 600-1400mum<2>, the standard deviation of the aperture area thereof is set to 1800mum<2> or less and the aperture ratio thereof is set to 15-40%. That is, when the average aperture area is too large, the way to issue of ink is non-uniform and, when the average aperture area is too small, missing dots are generated. When the aperture ratio is too large, ink is excessively issued locally and, when the aperture ratio is too small, the passage property of ink lowers.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art As a porous thin paper used as a heat-sensitive stencil sheet, (1) so-called Japanese paper made from natural fibers such as Kozo, Mitsumata and Manila hemp (Japanese Patent Publication No. 41-762) is used.
No. 3), (2) Paper made of recycled fibers or synthetic fibers such as rayon, vinylon, polyester, nylon and the like, (3) Natural fibers of the above (1) and recycled fibers or synthetic fibers of (2). Mixed paper made by mixing and
No. 18728), (4) So-called polyester paper obtained by hot-pressing thin paper made by mixing polyester fibers and unstretched polyester fibers as binder fibers with a hot roll (Japanese Patent Publication No. Sho 49-8809). ) Etc. are generally known.

Since such thin paper has a problem of functional deterioration due to deformation or dimensional change due to humidity or temperature, a proposal for reducing dimensional change when wet (Japanese Patent Laid-Open No. 61-254396). Alternatively, a proposal for a process in which a thin paper is impregnated with a synthetic resin liquid so that it can also function as an adhesive between the thin paper and the film (Japanese Patent Publication No. 55-47).
997), a proposal of high-quality thin paper obtained by combining a specific range of polyester fibers and a specific resin within a limited range (Japanese Patent Laid-Open No. 1-271293).
And so on. Further, in the case of polyester paper, a proposal regarding a detailed manufacturing method of how to make it excellent in dimensional stability and heat resistance (JP-A-58-76597)
JP-A-58-76598), a proposal for improvement by fine denier (JP-B-62-55999), and a proposal for improvement of rigidity (JP-A-2-67197).
And so on. Further, in the digital perforation method, it is proposed to improve the image quality by defining the aperture ratio, the average aperture area, etc. of the porous thin paper (Japanese Patent Laid-Open No. 2-33).
No. 0593). However, the high image quality (good ink permeability and good character resolution) that is the performance required for porous thin paper for heat-sensitive stencil used in fully automatic digital stencil printing machine with thermal head system, which has been rapidly growing recently. An image having excellent image quality, a uniform solid portion and little white spots) has not yet been obtained.

[0004]

The thin paper according to the prior art has the following problems. That is, since the opening area is large and the variation is large, the ink permeability is non-uniform, and the area where the ink is overprinted is set back (ink is printed on the back of the printed matter that is overlaid), and no ink is printed. A clear image cannot be obtained because the spots are white or dull. Japanese Patent Laid-Open No. 61-53092, which defines the opening ratio of thin paper.
In the case of the publication, it is effective for the perforability of the film,
Ink permeability is insufficient. Furthermore, JP-A-2
In the case of Japanese Patent No. 30593, the open area ratio, the average open area, and the compression work amount are specified, but the average open area is too large to satisfy the ink permeability.

The present inventor has conducted extensive studies to improve the above problems of thin paper used as a heat-sensitive stencil sheet, and as a result, by using fibers having a small average diameter and having an appropriate length, the aperture area is reduced. It has been found that a good image quality can be obtained by making the value smaller and the variation small.

[0006]

That is, the present invention is characterized in that the average opening area is 600 to 1,400 μm ² , the standard deviation of the opening area is 1800 μm ² or less, and the opening ratio is 15 to 40%. Is a thin paper for heat-sensitive stencil base paper. Less than,
The present invention will be described in detail.

In the present invention, the basis weight of the thin paper made into paper is 5 to 1
It is preferable that the thickness is 5 g / m ² and the thickness is 10 to 50 μm. More preferably, the basis weight is 8 to 13 g / m ² , and the thickness is 25.
˜40 μm and density of 0.25 to 0.45 g /
It is cm ³ . As described above, in order to uniformly extrude the ink through the holes of the film within the preferable basis weight and thickness range, a fine fiber (preferably 2 to 5 mm) having a preferable length (average fiber diameter of 2 to 12 μm) is used. By increasing the number of fibers used and dispersing the fibers uniformly, the voids of the thin paper can be appropriately subdivided, and the voids can be made as uniform as possible. Specifically, the average open area is 600-
The standard deviation of the open area in the 1,400μm ² is 1,800μ
m ² or less, the open area ratio is 15 to 40%, preferably
The average open area is 700 to 1,200 μm ² , the standard deviation of the open area is 1,200 μm ² or less, and the open area ratio is 18 to 30%.

If the average opening area is larger than 1,400 μm ² , the ink is not evenly ejected, and an image missing portion or an unclear portion is generated. On the other hand, if it is less than 600 μm ² , poor fiber dispersion occurs and white spots occur due to fiber flocs. Further, when the porosity exceeds 40%, the ink locally comes out excessively, and when viewed as a whole, it is not preferable because the dot connection of the characters is poor and the resolution is poor, and white spots in solid areas occur. If the porosity is lower than 15%, the ink permeability is poor, the dot connection of characters is poor, the resolution is poor, and white spots in solid areas are likely to occur, which is not preferable. In addition, the opening of the porous thin paper in the present invention is a portion where it seems that light is transmitted and forms a hole, and is a planar analysis of the hole through which the ink passes.

The fibers that make up the thin paper of the present invention include:
Any of natural fiber, regenerated fiber and synthetic fiber may be used, but preferably bast fiber such as Manila hemp and flax, regenerated fiber such as viscose rayon fiber, copper-ammonia rayon fiber, synthetic fiber such as nylon, polyester and vinylon. is there. These fibers may be made alone or may be mixed, but at least one of these fibers is preferably a fine fiber, and specifically, the average fiber diameter is 2 to 1.
Fibers with a moderate length of 2-5 mm in the range of 2 μm are preferred.

Papermaking of the thin paper according to the present invention is carried out by a method which is usually practiced. At this time, a dispersant and a sticking agent (preferably polyethylene oxide or polyacrylamide) used, a defoaming agent, a release agent, an antistatic agent, a paper-strengthening agent at the time of papermaking, and a sizing agent may be added. Needless to say. In the present invention, a so-called loose binder fiber may be used as a binder in the case of mixing a natural fiber and a synthetic fiber, but it is not preferable because the fiber diameter is large and the image quality is deteriorated. Binding by a coated material is preferable. As coating materials, viscose, polyvinyl acetate resin, acrylic resin, vinyl chloride resin, SB
There are synthetic rubbers such as R and NBR, urethane resins, epoxy resins, etc. Among them, both solvent solution type and emulsion type can be used, and the binding strength is strong and the film tension is small. ) Urethane resins and epoxy resins are preferred.

[0011]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. % In the examples and comparative examples represents% by weight.
In addition, the measurement and evaluation of the characteristics were performed by the following methods. (1) Opening analysis (average opening area, standard deviation of opening area, opening rate) Opening analysis is a high-definition image analysis file system IP-10.
00 (manufactured by Asahi Kasei Corp.). A magnifying device (PC printer 70) manufactured by Canon Inc. is used to make a 37x magnified copy (A4 size) of thin paper, and a reading magnification of 37 for a 6 cm x 7 cm area of an arbitrary portion.
Double, small figure removal: 180 μm ² or less The measurement was performed under the setting conditions, and from this, the average open area, the standard deviation of the open area and the open rate were automatically obtained. (2) Evaluation of image quality [Print unevenness] Amorphous copolyester film as heat-sensitive film (stretched thermoplastic synthetic resin film) (preferred over crystalline polyester film in terms of plate-making sensitivity) and the present invention Using a wet laminator with a thin laminating paper as a porous support of (2) using an adhesive for wet lamination (a solution in which isopropyl alcohol is used as a solvent and an epoxy compound and a polyamine resin are dissolved at a weight ratio of 17:83) A heat-sensitive stencil sheet (hereinafter referred to as a master) was used. Using this master, a thermal head test printing device (manufactured by Okura Electric Co., Ltd., thermosensitive coloring device TH-PMD) has a thermal head density of 400 dots / inch (manufactured by Toshiba Corp., TPH256R8).
Equipped with D), a 2 mm square small character, a fine line formed by 1 dot and 2 dots, and a pattern that can print a black solid part of 50 mm square with the optimum plate-making sensitivity are prepared by using a fully automatic digital stencil printer (ideal). RC manufactured by Kagaku Kogyo Co., Ltd.
It was printed at 115). The printed matter was evaluated by visual judgment. ○ indicates that there is no unevenness in the thickness of characters or thin lines or white spots on solid black, × indicates that the letters or thin lines are partially cut or have uneven thickness, and white spots are noticeable on solid black areas, △
Was set to a level between ○ and × that was practically usable.

[Gradation] The dot density is changed by using the above-mentioned printing device, the plate is made under the condition that an image having gradation is obtained, and the printed matter printed by the above-mentioned printing machine is evaluated by visual judgment. went. ∘ indicates that each dot is well reproduced, × indicates that the dots are notably visible, and Δ indicates an intermediate level between ◯ and × that is practically usable. (3) Basis Weight The mass of 10 test pieces (31.5 cm × 31.5 cm) that were allowed to stand at constant temperature (22 ° C.) and constant humidity (66% relative humidity) for 24 hours was measured. (4) Thickness Measured by JISP-8118

[0013]

Examples 1 to 3 (A) Manila hemp (raw hemp) was alkali-digested, washed, diluted with water to a concentration of 3%, and drained with a beater at 18 ° SR (JI
Manila hemp obtained by beating with SP-8121), and freeness 25 ° SR (JISP-182) obtained by disaggregating and bleaching pulp
The sisal of 1) was uniformly mixed with the synthetic fibers shown in Table 1 [fine denier polyester fibers: PET (A) to (B) and vinylon (A)] in the composition shown in Table 2 and epoxidized. The polyamide resin was added as an aqueous solution so as to be 2% with respect to the fibers, and added and mixed uniformly. Using this as a paper stock, thin paper was made with a circular rope paper machine. The thin paper was dried with a Yankee dryer having a drying temperature of 130 ° C. and wound. (B) Each thin paper obtained in (A) above was coated with a urethane resin (water-based emulsion: manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., Superflex 100) using a gravure coater. The coating amount was 1.0 g / m ² . (C) The basic properties and the properties (image quality) of the resin-processed thin paper obtained in (B) were evaluated, and the results shown in Tables 3 and 4 were obtained.

[0014]

Example 4 Manila hemp and sisal used in Examples 1 to 3 and fine denier polyester fibers shown in Table 1 [P
ET (C)] and vinylon fiber [vinylon (A)] are uniformly mixed in the composition shown in Table 2, and then thin paper is made into paper in the same manner as in (A) of Examples 1 to 3 and wound. Got a take roll. The evaluation of the basic properties and properties (imageability) of the resin-processed and resin-processed thin paper of this product were performed in the same manner as in (B) and (C) of Examples 1 to 3. The results are shown in Tables 3 and 4.

[0015]

COMPARATIVE EXAMPLE 1 Manila hemp used in Examples 1 to 3 and polyester fiber [PET (D)] shown in Table 1 were uniformly mixed in the composition shown in Table 2, and then the mixture of Examples 1 to 3 ( Thin paper was made into paper in the same manner as in section A) to obtain a winding roll. The evaluation of the basic characteristics and characteristics (imageability) of the resin-processed and resin-processed thin paper of this product were performed in Examples 1 to 3.
The same procedure as in (B) and (C) of was performed. The results are shown in Table 3,
It shows in Table 4.

[0016]

[Comparative Example 2] The thin paper of 100% Manila hemp used in Examples 1 to 3 was made into paper in the same manner as in (A) of Examples 1 to 3,
I got the winding roll. The evaluation of the basic properties and properties (imageability) of the resin-processed and resin-processed thin paper of this product were performed in the same manner as in (B) and (C) of Examples 1 to 3. The results are shown in Tables 3 and 4.

[0017]

Comparative Example 3 The thin paper of 100% sisal hemp used in Example 4 was made into paper in the same manner as in Examples 1 to 3 to obtain a winding roll. The evaluation of the basic properties and properties (imageability) of the resin-processed and resin-processed thin paper of this product were performed in the same manner as in (B) and (C) of Examples 1 to 3. The results are shown in Tables 3 and 4.

[0018]

[Table 1]

[0019]

[Table 2]

[0020]

[Table 3]

[0021]

[Table 4]

[0022]

INDUSTRIAL APPLICABILITY The present invention is a thin paper for a heat-sensitive stencil sheet having openings in a specific range, and the following excellent effects can be obtained. (1) The fibers are uniformly dispersed and the formation is good. (2) The perforating property of the film and the ink passing property are good, and the image at the time of printing is clear. (3) The ink does not overapply locally, and there is little set-off.

As described above, the porous support can have excellent performance.

Claims (1)

[Claims] 1. An average opening area of 600 to 1,400 μ
A thin paper for heat-sensitive stencil base paper, characterized in that it has a m ^{2 of 2} , a standard deviation of the opening area of 1,800 μm ² or less, and an opening ratio of 15 to 40%.