JPH05309967A - Porous thin paper for original paper for heat-sensitive stencile printing and preparation thereof - Google Patents

Abstract

PURPOSE:To obtain the title thin paper with neither white drop-out on the solid image part nor setoff by a method wherein a paper is made of a fiber wherein a polyvinyl acetal synthetic fiber being swellable and dissolvable in hot water is a main ingredient and it is brought into a specified water content and adhesion between fibers is formed within a specified thickness from the surface of one side by bringing the one surface into contact with a heating body. CONSTITUTION:A fiber wherein a polyvinyl acetal synthetic fiber with a thickness of at most 2.0 denier and a length of 2-10mm and being swelled or dissolved with hot water of at least 80 deg.C is a main ingredient is made into a paper by means of a paper-manufacturing machine 2. Then, water content is controlled to 50-80wt.% by means of a press roll 3 and adhesion between fibers is formed within 65% from the surface of one side by heating it for a short time at 80 deg.C or higher by means of a heating drum. A thermoplastic resin film with a thickness of at least 4mum is laminated on the side of the porous thin paper wherein there exists no adhesion between fibers. As the result, the title thin paper with high printing durability, less white drop-out on solid image parts and less setoff and good imaging properties can be obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a porous thin paper containing synthetic fibers as a main component, a method for producing the same, and a heat-sensitive stencil printing base paper using the thin paper.

[0002]

2. Description of the Related Art Conventional heat-sensitive stencil printing base papers are natural fibers such as hemp or polyester, polyvinyl acetal, synthetic fibers such as rayon, or porous thin paper such as a mixed paper thereof. , Vinylidene chloride-vinyl chloride copolymer resin film, vinyl resin film such as polypropylene film, and thermoplastic resin film such as polyester film are used.

The heat-sensitive stencil printing method is widely used because it is inexpensive and simple, but in recent years, higher printing quality has been demanded. However, in the case of plate making with a thermal head, for example, the thermal head has a higher density (e.g., 8 dots / mm has gone from 12 dots / mm to 16 dots / mm). There is a problem that the print quality cannot be improved because the performance of the base paper is not accompanied by it.

The required printing quality is that fine characters can be printed clearly, white spots are not present in the solid image portion, and the ink of the image printed with the stencil printing ink is transferred to the back surface of the next printing sheet. The so-called back ink is less likely to be so-called printing ink (if the ink permeability of the porous thin paper is too good, the back ink becomes terrible).

In order to solve the above-mentioned demands, improvement of printing clarity and elimination of white spots are described in JP-A-61-25.
Although 4396 describes that the number of fibers per unit area of the porous thin paper made of natural fibers is regulated, the porous thin paper by this technique has too good ink permeability and the ink permeation amount. However, it is not possible to control, and only printed matter with a lot of back reflection can be obtained.

Further, in JP-A-59-115898, a polyester fiber is mainly used, and a fibrous polyester fiber having a melting point lower than that of the main fiber is used as a binder.
Although the main fiber is not melted, but the binder fiber is heated at a temperature at which it is melted to form a fiber-fiber bond, the ink permeability can be suppressed by this method,
There is a problem that the printing is lacking in clarity.

In view of the above points, the present invention is a heat-sensitive stencil plate capable of clear printing even in a fine print image, having no white spots in a solid image, and controlling the amount of ink permeation so that back printing does not occur on the back side. An object of the present invention is to provide a porous thin paper for printing base paper, a method for producing the same, and a heat-sensitive stencil printing base paper using the porous thin paper as a support.

[0008]

Means for Solving the Problems That is, the present invention provides a porous thin paper mainly composed of non-crystallized synthetic fibers having a fiber thickness of 2.0 denier or less and a length of 2 to 10 mm. Is present within 65% of the thickness from the surface on one side, to a porous thin paper for heat-sensitive stencil printing base paper.

The present invention also relates to a papermaking paper having a fiber thickness of 2.0 denier or less, a length of 2 to 10 mm, and a polyvinyl acetal-based synthetic fiber which is swollen or dissolved by hot water of 80 ° C. or more as a main component. Of the water content of 50 to 80% by weight, one side is heated by contacting a heating body with a temperature of 80 ° C or higher to bond the fibers to each other within 65% of the thickness from the surface on one side. And a method for producing a porous thin paper for heat-sensitive stencil printing base paper.

The present invention is also a porous thin paper mainly composed of non-crystallized synthetic fibers having a fiber thickness of 2.0 denier or less and a length of 2 to 10 mm, wherein the interfiber adhesion is thick from one surface. The present invention relates to a heat-sensitive stencil printing base paper, characterized in that a thermoplastic resin film having a thickness of 4 μm or less is laminated on the side of the porous thin paper present within 65% of the thickness, which has no interfiber adhesion.

[0011]

OPERATIONS AND EXAMPLES The porous thin paper of the present invention is characterized in that the interfiber adhesion for enhancing the interfiber strength is unevenly distributed on one surface, and the interfiber strength of the porous thin paper is improved. If the binder fiber is used as in the conventional example to make it, or the binder resin is added to make paper, or the binder resin is impregnated in the post-processing step, there is interfiber adhesion in the entire porous thin paper. In this way, in the heat-sensitive stencil printing base paper in which a thermoplastic resin film is attached to this porous thin paper, the interfiber adhesion present at the adhesive interface between the porous thin paper and the film impedes the passage of ink, and the fine print image area is displayed. It was made based on the knowledge that the image quality becomes unclear and that the solid print part has a white part (so-called white gap) where ink does not get on, which causes deterioration of print quality. Than it is.

In the heat-sensitive stencil printing base paper of the present invention in which the thermoplastic resin film is laminated on the surface of the porous thin paper where the interfiber adhesion is unevenly distributed on one side, the interfiber adhesion is present. When the ink is supplied from the side, the ink fills the non-fiber side where the films are laminated and moves through the perforated holes in the film onto the printing paper. At this time, since the amount of ink permeation is controlled on the side where the fiber-to-fiber adhesion is present, back transfer is prevented, and ink can be sufficiently supplied to the surface of the perforated film holes. The phenomenon of white transparency hardly occurs.

As the raw material fibers used in the porous thin paper of the present invention, non-crystalline synthetic fibers such as polyvinyl acetal type, polyester type, acrylic type and rayon can be used as a main component. Synthetic fibers are preferable to natural fibers because their cross-sections and fiber lengths are almost uniform, and porous thin paper with less variation can be easily obtained. The fibers may be used alone or in combination of two or more.

Among the above-mentioned synthetic fibers, after polyvinyl alcohol is spun, polyvinyl acetal fibers, such as vinylon fibers, which are acetalized with formaldehyde, benzaldehyde or the like and swelled or dissolved in hot water, such as vinylon fibers, are easily interfiber-bonded. From the point, it is particularly preferable.
In the case of the vinylon fiber, when it is momentarily heated in the presence of water, it partially swells or dissolves, which forms an interfiber bond and strengthens the interfiber strength.

The raw fiber has a thickness of 2.0 denier or less, preferably 0.2 to 1.5 denier, and a length of 2 to 10 m.
It is preferable that the main component is m, preferably 3 to 7 mm. When the thickness of the fibers exceeds the above range, the passage of ink in the obtained heat-sensitive stencil printing base paper is not controlled, and the back slippage increases. If the length of the fiber is less than the above range, the entanglement of the fiber is small and the papermaking is difficult, which is not preferable. If the amount exceeds the above range, the fiber dispersion during papermaking becomes poor, and the sharpness is lowered due to so-called fiber binding, which is not preferable.

The fiber-to-fiber adhesion needs to be within 65% of the thickness from the surface on one side to the inside. If the interfiber adhesion exceeds the above range, the ink permeability will be poor and the printing will lack clarity. In addition, it is preferable that the interfiber bonding is present from the surface on one side to the range of at least 25% of the thickness. If the inter-fiber adhesion is less than the above range, the strength will be reduced and unbonded fibers will fall off, or the obtained porous thin paper can be pasted with a thermoplastic resin film to obtain the printing durability of the stencil printing base paper. It is not preferable because the force becomes small.

The distribution density of the inter-fiber adhesion may be uniform from the surface to the inside, or may have a gradient such that the closer it is to the surface, the higher the distribution density becomes.

It is preferable that each of the interfiber bonds has substantially the same area, but in reality variations occur. In practice, the adhesive area per adhesive point is 0.4 mm ² or less,
Particularly, it is preferably 0.3 mm ² or less. The number of bonding points for inter-fiber bonding also varies depending on the thickness of the fiber and therefore cannot be specified unconditionally, but normally the average number of bonding points per 100 mm ² is 100 or more, preferably about 150 to 500. The number of bonding points per unit area may vary depending on the depth from the surface, but as a whole in this specification, 1
It is expressed as an average value per 00 mm ² .

If the adhesion area per one adhesion point exceeds the above range, the ink permeability deteriorates and the sharpness of printing is deteriorated, which is not preferable. The lower limit of the adhesive area per adhesive point cannot be unconditionally specified because it varies depending on the thickness of the fiber, etc., but it is usually preferably 2 × 10 ⁻⁵ mm ² or more from the viewpoint of ^obtaining the desired interfiber adhesive strength. .. If the number of the adhesion points is less than the above range, the strength becomes small, and if it exceeds the above range, the ink permeability is deteriorated and the sharpness of printing is deteriorated, both of which are not preferable.

The thickness and basis weight of the porous thin paper of the present invention are not particularly limited, but usually the thickness is 30 to 65 μm and the basis weight is 7 to 15 g.
/ m ² is suitable.

In order to produce the porous thin paper of the present invention, a fiber containing non-crystallized synthetic fibers as a main component is made into a paper, and subsequently an interfiber bond is produced. Most preferably, the interfiber bonding is by heat.

That is, when the synthetic fibers are paper-made by a usual method and the moisture content is adjusted and then heated from one side for a short time, inter-fiber adhesion occurs up to a certain depth from the heated surface, and the other is not heated. No inter-fiber adhesion occurs on the surface side of the.

In the method of forming the interfiber bond by heat,
Since the adhesion depth can be adjusted by adjusting the water content, it is possible to obtain the optimum porous thin paper for heat-sensitive stencil printing base paper, and it is possible to make a continuous continuous process from papermaking to winding. It is also preferable in terms of cost.

The non-crystalline synthetic fiber is particularly preferably one that swells or dissolves in hot water of 80 ° C. or higher in order to form the interfiber bond by the heat. Synthetic fibers that swell or dissolve at a low temperature of less than 80 ° C. are not preferable because a slight amount of heat during processing tends to cause inter-fiber adhesion and the risk of quality change due to heat even after being made into a product. Examples of the fibers that swell and dissolve in the hot water include the polyvinyl acetal fibers described above.

A method for producing the porous tissue paper of the present invention is described below.
Hereinafter, description will be given with reference to the drawings.

FIG. 1 is a schematic view showing a paper making process of the porous thin paper of the present invention. In FIG. 1, 1 is the raw material,
It is a stock stock inlet of a paper stock in which non-crystallized synthetic fibers having a length of 2.0 denier or less and a length of 2 to 10 mm, for example, polyvinyl acetal fibers are dispersed in water.

The paper stock is supplied to the paper machine 2 and paper is made by a conventional method. The supply amount of stock is usually 30 ~ 65μm,
Adjusted to give a final product with a basis weight of 7-15 g / m ² . As the paper machine, various types of paper machines can be used, for example, a short-net paper machine and a round-net paper machine, and in some cases, two or more types of paper machines such as a paper machine having a round-net and a short-net. Machines may be used in combination.

The wet paper obtained on the paper machine is press roll 3
It is dehydrated to a moisture content of 50-80% by weight.
The amount of this water is important because the depth of inter-fiber adhesion described below can be controlled by adjusting this amount.
It is determined within the above range in consideration of the temperature at which the fibers are swollen or dissolved by hot water, the maximum area of interfiber adhesion to be set, and the number of adhesion points per 100 mm ^{2 of} interfiber adhesion.

If the water content is less than the above range, the bonding area per fiber-bonding and the number of bonding points per 100 mm ² are small and the strength is weak, which is not preferable. If it exceeds the above range, the adhesive area per one fiber-to-fiber bond becomes larger than 0.4 mm ^2, and the fiber-to-fiber bond in the thickness direction also exceeds 65%, so that the printing definition becomes poor, which is not preferable.

The papermaking paper whose moisture content has been adjusted by the press roll 3 is then transferred onto the cylindrical rotary heating drum 4 and heated from the surface side of the drum to 80 ° C. or higher to the surface side in contact with the drum. The fiber-to-fiber bond can occur within 65% of the inside. The heating temperature needs to be 80 ° C. or higher,
The temperature is usually about 100 to 150 ° C., but it is appropriately set in consideration of the heating time. The heating time is usually about 2 to 20 seconds. However, the heating time is variously changed depending on the papermaking speed, the moisture content, and the heating temperature, and is not limited to this range.

The porous thin paper bonded between fibers by heating is then wound up by the winder 5 through the usual post-treatment process in ordinary papermaking.

The above-mentioned porous thin paper is made into the heat-sensitive stencil printing base paper of the present invention by laminating a thermoplastic resin film having a thickness of 4 μm or less on the side where there is no inter-fiber adhesion.

The thermoplastic resin film used in the heat-sensitive stencil printing base paper of the present invention is not particularly limited, and depending on the film perforation method such as thermal head or infrared irradiation, the film perforation energy is further increased. Is appropriately selected according to Generally, a biaxially stretched thermoplastic resin film, for example, a polyethylene terephthalate film having a stretching ratio of 150 to 250% in the longitudinal and transverse directions, a copolyester film, a polyethylene film, a vinyl chloride-vinylidene chloride copolymer film, etc. Any film can be used.

The thickness of the film is selected within the range of 4 μm or less, preferably 1 to 3 μm, so as to ensure the perforation by heat, in consideration of the perforation method and the perforation energy.

For example, in the case of plate making with a thermal head, usually, a biaxially stretched polyethylene terephthalate film having a thickness of 2 to 3 μm is preferably used. However, if the applied energy to the thermal head is less than 0.1 mJ / dot, the thickness should be about 1.5 to 1.8 μm, or the heat shrinkage with higher sensitivity (value after heat treatment at 150 ℃ × 30 minutes). 5% or more of polyethylene terephthalate film and low melting point polyester film are used.

Examples of the adhesive used for adhering the thermoplastic resin film to the porous thin paper include polyester resins, acrylic resins, vinyl acetate resins, urethane resins and the like. The amount of the adhesive applied is preferably about 0.2 to 1.0 g / m ² in terms of dry weight. If the dry coating amount of the adhesive is less than the above range, the adhesive strength will be reduced, and if it is more than the above range, the printing definition will be reduced, which is not preferable.

In order to adhere the thermoplastic resin film to the porous thin paper, an adhesive is usually applied to the thermoplastic resin film side, and the surface of the porous thin paper without interfiber adhesion is superposed thereon. Bond and heat dry.

The present invention will be specifically described with reference to experimental examples, but the present invention is not limited to these.

Experimental Examples 1 to 6 and Comparative Experimental Example 1 Vinylon fibers alone (Experimental Examples 1 and 6 and Comparative Experimental Example 1), a mixture of two kinds of vinylon fibers having different thicknesses and lengths (Experimental Examples 2 and 3), A mixture of vinylon fibers and polyester fibers (Experimental Example 4) and a mixture of vinylon fibers and acrylic fibers (Experimental Example 5) were paper-made by a round-paper machine in accordance with a conventional method. The papermaking speed was 50 meters per minute. The wet paper thus obtained was dehydrated with a press roll to adjust the water content, and heated at 110 ° C. for 15 seconds from the drum surface side with a rotary heating drum to obtain a porous thin paper.

The type and thickness of the fibers used, the length, the mixing ratio (% by weight) of the mixture, the moisture content before heating (% by weight), the thickness and basis weight of the obtained porous thin paper. Table 1 shows the depth of interfiber bonding (relative to thickness), the maximum area per interfiber bond, and the average number of interfiber bonds per 100 mm ² .

Depth of adhesion between fibers (relative to thickness)
And the maximum area per fiber bond, between fiber bonds
The average number per 100 mm ² was measured as follows.

Depth of Interfiber Adhesion Since the paper layer peels at the interface between the portions where interfiber adhesion is present and the portions where interfiber adhesion is not present, the depth of interfiber adhesion was measured using this phenomenon. That is, a cellophane tape is attached to the side where there is no interfiber adhesion, and when it is peeled off, a paper layer with no interfiber adhesion is attached to the cellophane tape side, and the remaining is the paper layer with interfiber adhesion ( Let B be the thickness of this layer). When the original paper thickness is A, the fiber adhesion depth is B / A × 100.

Maximum area per one fiber-to-fiber adhesive observed with an optical microscope (magnification 50 times) and measured. The dimensions were measured with an eyepiece-mounted micrometer.

Average number of interfiber bonds per 100 mm ² The number of interfiber bonds was measured by observing with an optical microscope (magnification 50 times).

Comparative Experimental Example 2 Manila hemp pulp was used as the fiber, the thickness was 43 μm, and the basis weight was 11.
2 g / m ² of Manila hemp 100% by weight porous thin paper was obtained.

[0046]

[Table 1]

Experimental Examples 7 to 12 and Comparative Experimental Example 3 On the surface of the porous thin paper obtained in Experimental Examples 1 to 6 and Comparative Experimental Example 1 where there is no interfiber adhesion, a thickness of 1.8 μm, 150 ° C. × 30 minutes later. Of a biaxially stretched polyethylene terephthalate film with a heat shrinkage of 10%, and a polyester resin adhesive at 0.5 g / m ²
It was used and adhered to produce a heat-sensitive stencil printing base paper.

Comparative Experimental Example 4 The biaxially stretched polyethylene terephthalate film used in Experimental Example 7 was similarly adhered to the surface of the porous thin paper obtained in Experimental Example 5 with the interfiber adhesion, and the heat-sensitive stencil printing base paper was prepared. Was manufactured.

Comparative Experimental Example 5 The biaxially stretched polyethylene terephthalate film used in Experimental Example 7 was similarly adhered to the porous thin paper of Manila hemp obtained in Comparative Experimental Example 2 to produce a heat-sensitive stencil printing base paper.

The heat-sensitive stencil printing base paper thus obtained was made into a plate using a Duplo Digital Plate Making Machine DP-3090 manufactured by Duplo Co., Ltd., and printed for evaluation.

The evaluation items, their methods and criteria are as follows.

White part of solid image part: A black image part of an obtained printed matter is printed by using a manuscript in which a white square having a side of 20 mm and a black square are arranged in a checkered pattern, and using the original. The white spots that were confirmed in Table 1 were measured.

A: A solid image area of 400 mm ² has less than 5 white spots of 0.2 mm ² or more.

B: There are 5 or more and less than 10 white spots of 0.2 mm ² or more in the solid image area of 400 mm ² .

C: There are 10 or more white spots of 0.2 mm ² or more in the solid image area of 400 mm ² .

Back transfer: A plate made of a white square and a black square with a side of 20 mm arranged in a checkerboard pattern is used to make a plate, which is used to print on a commercially available PPC paper to obtain 50 prints and to be printed. The degree of transfer of the printing ink to the surface was visually judged.

A: There is almost no back slipping.

B: There is some back slipping.

C: There is a lot of back slipping.

Image characteristics The facsimile test chart No. 2 manufactured by The Institute of Image Electronics Engineers of Japan was used as a document for plate making, and printing was performed using the obtained document. The obtained printed matter had reproducibility of characters, continuity of ruled lines, and solid image portion. The overall evaluation of the white spots of

A: Good B: Normal C: Poor Number of prints: A 0.5 mm thick, 240 mm long solid line drawn at 10 mm intervals is used to make a plate, and printing is performed using this to make a solid line. The number of printed sheets when the difference in thickness or ruled line interval was 3% or more was defined as the number of printed sheets.

The evaluation results are shown in Table 2.

[0063]

[Table 2]

From Table 2, it can be seen that, in the stencil printing using the heat-sensitive stencil printing base paper of the present invention, the number of printable sheets is large, there are few white spots in printing solid images, and the back printing of the printing ink is small, and the image quality is good. ..

[0065]

EFFECTS OF THE INVENTION In stencil printing using the heat-sensitive stencil printing base paper of the present invention, the number of printable sheets is large, there are few white spots and back-printing of printing ink in solid printing, and image quality is good.

[Brief description of drawings]

FIG. 1 is a schematic view showing a papermaking process of porous thin paper.

[Explanation of symbols]

 2 Paper machine 3 Press roll 4 Heating drum

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor ▲ Hiro ▼ Se Sho Riku 529 Takaoka-cho, Tosa City, Kochi Prefecture ▲ Hiro ▼ Se Paper Co., Ltd. (72) In Hitoshi Ito 529 Takaoka-cho, Tosa City, Kochi Prefecture Address ▲ Hiro ▼ Se Paper Co., Ltd.

Claims (8)

[Claims] 1. A porous thin paper mainly composed of non-crystallized synthetic fibers having a fiber thickness of 2.0 denier or less and a length of 2 to 10 mm, wherein the interfiber adhesion is 65 from the surface on one side. % Of the porous thin paper for heat-sensitive stencil printing base paper. 2. The porous thin paper according to claim 1, wherein the adhesive area per one fiber-to-fiber bond is 0.4 mm ² at maximum, and the number of fiber-to-fiber bonds is 100 or more per 100 mm ^{2 on} average. 3. The porous thin paper according to claim 1, wherein the synthetic fiber is a polyvinyl acetal-based synthetic fiber, and the interfiber bonding is by thermal bonding. 4. A papermaking paper having a fiber thickness of 2.0 denier or less, a length of 2 to 10 mm, and a polyvinyl acetal-based synthetic fiber as a main component which swells or dissolves in hot water of 80 ° C. or more. , If the moisture content is in the range of 50 to 80% by weight, one side is heated by contact with a heating body at a temperature of 80 ° C or higher to form an interfiber bond within 60% of the thickness from the surface on one side. A method for producing a porous thin paper for heat-sensitive stencil printing base paper, which is characterized in that 5. The method for producing a porous thin paper according to claim 4, wherein the adhesive area per one fiber-to-fiber bond is 0.4 mm ² at the maximum, and the number of fiber-to-fiber bonds is 100 or more per 100 mm ^{2 on} average. 6. A porous thin paper mainly composed of non-crystalline synthetic fibers having a fiber thickness of 2.0 denier or less and a length of 2 to 10 mm, wherein the inter-fiber adhesion has a thickness of 65 from one surface. %, A thermoplastic resin film having a thickness of 4 μm or less is laminated on the side of the porous thin paper where there is no interfiber adhesion, and the heat-sensitive stencil printing base paper is characterized. 7. The heat-sensitive stencil printing paper according to claim 6, wherein the adhesive area per one fiber-to-fiber bond is 0.4 mm ² at maximum, and the number of fiber-to-fiber bonds is 100 or more per 100 mm ^{2 on} average. 8. The heat-sensitive stencil printing base paper according to claim 6 or 7, wherein the synthetic fiber is a polyvinyl acetal-based synthetic fiber, and a porous thin paper in which interfiber bonding is by thermal bonding is used.