JPH11129643A - Base-paper for thermal stencil printing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a base-paper for thermal stencil printing in which printing properties are excellent and furthermore both traveling properties in a printing press and economical efficiency are excellent. SOLUTION: The base-paper for thermal stencil printing is formed by sticking a thermoplastic resin film to a porous supporting body consisting of thermoplastic resin and fiber without substantially using an adhesive. At least one part of fiber constituting the porous supporting body forms a paddle-shaped film consisting of a polymer which extends over a plurality of fibers and constitutes the fiber, and area rate of the paddle-shaped film is 8-80%. Further, the full surface is printed over all into black by a stencil printing press. The number of a void part, in which the diameter of a minimum circumscribed circle in the void part out of the void faults on printed matter is >=1 mm, is <=100 pieces per 10 m<2> printing area.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive stencil sheet to be perforated by a thermal head or the like. More specifically, the present invention relates to a stencil sheet for heat-sensitive stencil printing which is excellent in printing quality and excellent in handling property and passing property in a printing machine.

[0002]

2. Description of the Related Art Conventionally, as heat-sensitive stencil base paper,
A porous substrate composed of natural fiber, synthetic fiber or synthetic fiber or thin paper, non-woven fabric, gauze, etc., made of natural fiber, chemical fiber or synthetic fiber, or a mixture of these, is bonded to a thermoplastic resin film such as polyester film, vinylidene chloride film or polypropylene film with an adhesive. Known structures are known.
For example, Japanese Patent Application Laid-Open No. 59-2896 discloses a thin paper for heat-sensitive stencil paper characterized in that it contains 50% by weight or more of polyester short fibers having a circular or nearly circular cross section in order to improve perforation. . However, according to the study by the present inventors, if the fiber diameter is smaller than 30 μm, there is no substantial difference in the bonding area between the fiber and the film even if the fiber cross section is circular or flat, and there is no difference in the perforation characteristics. I couldn't. In addition, in order to produce thin paper made of polyester staple fibers, an adhesive is required as a binder between the fibers as described in Examples, and this adhesive component prevents ink permeation during printing and impairs printability. May cause a decrease.
On the other hand, in the absence of the binder component, the adhesion between the fibers is insufficient, and the rigidity of the support is reduced, the yield at the time of lamination with the film is reduced, and poor printing due to the reduced running property in a printing machine is caused. .

[0003] Japanese Patent Application Laid-Open No. 3-76894 discloses a technique in which the bending rigidity is set to a certain value or more in order to prevent the occurrence of wrinkles and wrinkles when the film and the support are bonded and to prevent the fibers from falling off in the printing machine. ing. As a specific technique, a method is disclosed in which polyester short fibers are mixed with undrawn binder fibers, papermaking is performed, and then thermocompression bonding is performed. However, this technique requires many steps of fiber spinning, (drawing), cutting, mixing, papermaking, thermocompression bonding, lamination with a film, and many steps before forming a support. Since the binder fibers are melted and deformed during the thermocompression bonding process and impede the transmission of ink, the printability is deteriorated.

[0004]

In recent years, heat-sensitive stencil printing has tended to have higher resolution and higher sensitivity. Even in heat-sensitive stencil printing paper, the perforation sensitivity has been improved for films and for stencils for supports. Improvements in ink permeability and rigidity are required. In order to improve the perforation sensitivity of the film, a method of thinning the film is generally used, and in order to improve the ink permeability of the support, there is a method of thinning the support. Will reduce the stiffness. For this reason, there is a strong demand for achieving both high precision printing and rigidity of the base paper.

The present invention has been made in view of the above technical background, and has as its object to provide a heat-sensitive stencil sheet which is excellent in printability and excellent in running property and economy in a printing press.

The present invention employs the following means in order to solve the above problems. That is, the heat-sensitive stencil printing base paper of the present invention is a thermoplastic resin film and a porous support made of thermoplastic resin fibers,
A base paper for thermosensitive stencil printing which is bonded substantially without an adhesive, wherein at least a part of the fibers constituting the porous support member spans a plurality of fibers to constitute the fibers. Forming a web-like film consisting of
Further, the area ratio of the web-like film is 8 to 80%, and among the white spot defects on the printed matter obtained by performing the black solid printing by the stencil printing machine, the diameter of the minimum circumscribed circle of the white spot is 1 mm.
The number of white spot defects described above is 10 per 10 m ^{2 of} print area.
The number is not more than 0.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention has been studied diligently for heat-sensitive stencil printing paper excellent in printability and runnability in a printing machine. As a result, a specific porous support made of thermoplastic resin fibers is formed on a thermoplastic resin film. By using a composite sheet in which the bodies are joined, it has been found that such a problem can be solved at once.

The thermoplastic resin in the present invention is not particularly limited, but includes polyolefin resins such as polyethylene and polypropylene; polyester resins such as polyethylene terephthalate, polybutylene terephthalate and polyethylene naphthalate; nylon 6 and nylon 66. And melt-moldable resins such as polyamide resins and polyphenylene sulfide resins. Among them, polyester resins, particularly polyethylene terephthalate, are preferably used in terms of balance between economy and physical properties. If necessary, these resins may be copolymerized with other components up to 30% of the repeating unit. Flame retardants, heat stabilizers, antioxidants, ultraviolet absorbers, antistatic agents, pigments , A dye, a fatty acid ester, an organic lubricant such as wax, or an antifoaming agent such as polysiloxane. Examples of such a copolymer component include an isophthalic acid component in the case of polyethylene terephthalate. Furthermore, lubricity can be imparted depending on the application. The method for imparting lubricity is not particularly limited. For example, clay, mica, titanium oxide, calcium carbonate, kaolin, talc, inorganic particles such as wet or dry silica, acrylic acids, organic materials containing styrene, etc. A method of blending particles and the like, a method of so-called internal particles for precipitating a catalyst and the like to be added during the polyester polymerization reaction, a method of applying a surfactant, and the like can be employed.

The thermoplastic resin constituting the film and the long-fiber nonwoven fabric of the present invention may be the same or different. However, in view of the thermal adhesiveness between the two, it is preferable that the thermoplastic resins are of the same type. .

[0009] The thermoplastic resin film of the present invention needs to be biaxially stretched. Unstretched or uniaxially stretched films are not preferred because of insufficient mechanical strength and poor printing durability. Further, in order to obtain a high-definition printing pattern, the thickness of the film is 0.2 to 5.0 μm.
Is more preferable, and more preferably 0.5 to 3.0 μm. In addition, the melting point of the film is preferably lower than the melting point of the nonwoven fabric for good perforation.

The porous support made of thermoplastic resin fibers in the present invention may be a nonwoven fabric made of short fibers, a nonwoven fabric made of long fibers, or any other nonwoven fabric. Advantageously, it is an advantageous long-fiber nonwoven fabric. As the long-fiber nonwoven fabric, for example, after heating and melting the above-described thermoplastic resin, a fiber spun from a die is pulled by an ejector and opened by an impact plate, and a spunbond nonwoven fabric obtained by fusing the fibers by thermocompression bonding or the like, Alternatively, a melt-blown nonwoven fabric or the like formed on the collection surface by spraying high-temperature and high-pressure air onto the melt extruded from the die to perform fiber formation and nonwoven fabric formation at once can be used. preferable. The lower the intrinsic viscosity (IV) of the nonwoven fabric, the easier it is to stretch. However, when the intrinsic viscosity is 0.40 or less, the spinnability is significantly reduced.
Is preferable, 0.40 to 0.60 is more preferable, and 0.
More preferably, it is 44 to 0.55.

The heat-sensitive stencil printing paper of the present invention needs to adhere a non-woven fabric made of a thermoplastic resin and a thermoplastic resin film without substantially interposing an adhesive which inhibits ink transmission during printing. . As a bonding method without using an adhesive, there is a method in which the film and the nonwoven fabric are fused and integrated by heat. In particular, a method in which the unstretched film and the nonwoven fabric are thermocompressed and then stretched and thermally fused together is preferable because the adhesive strength is strong. In this case, when a polyethylene terephthalate nonwoven fabric is used as the nonwoven fabric, the birefringence of the fibers constituting the nonwoven fabric is set to 0.0
It is preferably 20 or less, more preferably 0.008 or less, and most preferably substantially non-oriented.

The porous support of the present invention has an area ratio of the web-like film spanning a plurality of fibers of 10% or more, preferably 15% or more, and more preferably 20% or more. When the area ratio of the web-like film is smaller than 8%, the strength and rigidity of the porous support tend to be inferior. Further, if the area ratio of the web-like film exceeds 80%, ink transmission becomes poor, so that the area ratio of the web-like film is 80% or less, preferably 70% or less. Here, the web-like film is a film in which at least a part of the fibers constituting the porous support is formed of a polymer constituting the fibers over a plurality of fibers, and is a scanning type from the support side. It can be observed using an electron microscope. Specifically, unstretched or semi-stretched fibers are laminated on a film, and after pressure bonding, the film is stretched in at least one direction, preferably biaxially, so that the fibers are stretched, A web-like coating is formed between the joined fibers.

The area ratio of the web-like film is a value expressed as a percentage of the ratio of the area of the web-like film to the area of the heat-sensitive stencil printing paper observed from the support side with a scanning electron microscope. The area of the fiber not directly bonded to the web-like film is not included in the area of the web-like film.

The heat-sensitive stencil printing paper of the present invention is characterized in that, among the white spots on a printed material obtained by performing solid black printing on a stencil printing machine, the white spot defect in which the minimum circumscribed circle of the white spot is 1 mm or more. It is characterized in that the number is 100 or less, preferably 50 or less, more preferably 10 or less per 10 m ^{2 of} printing area. The number of white spot defects is 10
If the number exceeds 100 per m < ² >, the print quality tends to be inferior.

Normally, when the area ratio of the web-like film increases,
Although the white spot defect increases and the print quality is inferior, the inventors of the present invention have studied and found that the presence of the web-like film at a position distant from the film surface does not hinder the ink transmission. It has been found that it is possible to increase the strength and rigidity. When the web-like film is not in contact with the film surface, it is presumed that the ink has reached the film surface so as to wrap around from the periphery of the web-like film, and printing has been possible without causing white spot defects.

As a method of causing the web-like film to be present at a position away from the film surface, for example, when the film of the heat-sensitive stencil printing paper is bonded to the support nonwoven fabric,
This can be achieved by setting the preheating temperature on the film surface side lower than the preheating temperature on the support nonwoven fabric side.

Next, an example of a method for producing a heat-sensitive stencil sheet of the present invention will be described with reference to FIGS. That is, FIG. 1 is a schematic view of a manufacturing process of a melt-blown nonwoven fabric which is a porous support constituting the heat-sensitive stencil printing base paper of the present invention. As shown in this figure, a molten thermoplastic polymer is discharged from a plurality of orifices (1) arranged in a row, and a heated gas is supplied to the discharged molten polymer from slits provided on both sides of the orifice row. Sprayed obliquely and thinned into a fiber form, collected in a sheet on the lower collecting conveyor surface (2) and melt-blown non-woven fabric (3)
Can be obtained.

On the other hand, FIG. 2 is a schematic view of the production process of the heat-sensitive stencil sheet of the present invention. As shown in FIG.
A thermoplastic resin melted from a die (4) by a die extrusion method is extruded onto a cast drum (5) to form an unstretched film, laminated with the nonwoven fabric (3) obtained as described above, and then glass transition of the nonwoven fabric. Preheating and temporary bonding are performed by passing through a plurality of roller groups (6) heated to a temperature equal to or higher than the temperature. At this time, the temperature of the roller in contact with the nonwoven fabric of the rollers of the roller group (6) is set higher than the temperature of the film. Subsequently, the laminate is stretched longitudinally at a temperature equal to or higher than the glass transition point between a pair of rollers (7), and subsequently transversely stretched in a tenter stretching machine (8) at a temperature equal to or higher than the longitudinal stretching. To obtain a heat-sensitive stencil sheet (9) of the present invention.

[0019]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to Examples.

The physical properties shown in the examples are obtained by the following measuring methods.

<Intrinsic Viscosity IV> Measured at 25 ° C. using orthochlorophenol as a solvent.

<Density (g / m2)> 20 cm × 20 cm
The weight of each sample was measured and converted to the weight per 1 m ² .

<Area ratio of web-like film> The heat-sensitive stencil sheet was taken from the porous support side in an area of 1c by a scanning electron microscope.
Shoot m2 or more. The photograph was taken using a CCD camera and a personal image analysis system LA-52 manufactured by Pierce Co., Ltd.
5 and the area ratio of the webbed portion was measured. When it was difficult to distinguish the webbed portion, the webbed portion on the photograph was colored white in advance and measured.

<Number of white spot defects> A commercially available thermosensitive stencil printing machine (Riso Kagaku Kogyo Co., Ltd.)
And GR375), 20 prints were made on the same plate using the same printing plate, white spots were observed on the twentieth printed matter, and the number of white spots whose minimum circumscribed circle exceeded 1 mm was measured. This was repeated for 1 m ² of the heat-sensitive stencil printing base paper and converted into the number of defects per 10 m ² .

<2% tensile strength> Toyo Baldwin Co., Ltd.
Using Tensilon UTM-III manufactured, the strength and elongation curve of a sample having a width of 1.5 cm and a length of 5 cm were measured in the winding direction. The strength at 2% elongation of the obtained curve was defined as 2% tensile strength.

<KES type bending stiffness B value> K by Kato Iron Works
It measured with the ES-FB2 pure bending tester. Front bending (+ K)
And the average value of back bending (-K) was used. Note that the vertical direction refers to the winding direction of the film, and the horizontal direction refers to a direction orthogonal to the vertical direction.

Examples 1 and 2 A polyethylene terephthalate polymer having an IV = 0.48 was prepared at 285 ° C. using a spinning machine equipped with a melt-blowing injection device having 10 orifices per cm of a die and a gas injection slit gap of 2.0 mm. Melted and extruded from orifice, pressure 2 kg / cm ² G on gas injection slit
Injected onto a collecting conveyor installed at a distance of 40 cm with the heated air of about 300 degrees supplied by
Was obtained. At this time, the distance between the die and the collecting conveyor was adjusted so that the surface temperature of the nonwoven fabric immediately after being sprayed onto the collecting conveyor was 95 ° C. The obtained nonwoven fabric was composed of substantially non-oriented fibers. On the other hand, as a film, a 25 mol% copolymerized polyethylene terephthalate (IV = 0.65) chip of isophthalic acid was used as an extruder having a screw diameter of 40 mm. Cast on top to make an unstretched film. The above melt blown nonwoven fabric was laminated on an unstretched film, and preheated through four preheating rolls (A to D). At this time, the two rolls (B, D) in contact with the film surface were set at 85 ° C, and the two rolls (A, C) in contact with the nonwoven fabric surface were set at 95 ° C. 2. between the stretching rolls heated to 90 ° C. in the longitudinal direction.
After stretching 5 times, it is sent to a tenter type stretching machine,
Stretched 3.7 times in the width direction, and further 160
° C. × 5 seconds and heat-treated to give a film thickness of 1.0 .mu.m, a heat-sensitive stencil sheet having a basis weight of 10.5 g / m ² of the support non-woven fabric. At this time, Examples 1 and 2 and Comparative Examples 1, 2, and 3 were prototyped by setting the set temperature of the preheating roll as shown in Table 1.

[0028]

[Table 1] Table 1 shows the properties of the obtained heat-sensitive stencil printing base paper. Example 1 was a heat-sensitive stencil sheet having few printing defects and sufficient mechanical properties, and Example 2 was a heat-sensitive stencil sheet having particularly small printing defects and excellent printability. Further, Example 3 was a heat-sensitive stencil sheet having particularly excellent mechanical properties. On the other hand, Comparative Example 1 was excellent in mechanical properties but generated a large amount of webbing, had many printing defects, and was inferior in print quality. Comparative Example 2 Sufficient stretching could not be performed due to insufficient preheating of the support nonwoven fabric, and a heat-sensitive stencil sheet could not be obtained.

Examples 4-5, Comparative Example 3 Except for adjusting the distance between the die and the collection conveyor so that the temperature of the nonwoven fabric immediately after being sprayed on the collection conveyor was 90 ° C, 100 ° C and 110 ° C, respectively. In the same manner as in Example 1, Examples 4 and 5 and Comparative Example 3 were obtained.

Of the obtained heat-sensitive stencil printing papers, Examples 4 and 5 were excellent in printing quality and mechanical properties, respectively, while Comparative Example 3 was excellent in mechanical properties but lacked white spots. Base paper with poor printing quality.

[0031]

[Table 2]

[0032]

According to the heat-sensitive stencil printing paper of the present invention, by setting the area ratio of the web-like film straddling a plurality of fibers in the support within a certain range, there is little white spot defect on printed matter due to poor ink transmission. It has excellent printing properties that are not achieved with conventional heat-sensitive stencil printing base paper, while having excellent mechanical properties as heat-sensitive stencil printing base paper while having the characteristics described above.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an example of a production process of a melt-blown nonwoven fabric as a porous support constituting the present invention.

FIG. 2 is a schematic process diagram showing an example of a process for producing a heat-sensitive stencil sheet of the present invention.

[Explanation of symbols]

 1: Melt blow die 2: Collection conveyor 3: Melt blow nonwoven fabric 4: Film die 5: Cast drum 6: Preheating roller group (A, B, C, D) 7: Vertical stretching zone 8: Horizontal stretching zone 9: Thermal stencil printing Base paper

Claims (4)

[Claims] 1. A heat-sensitive stencil printing paper comprising a thermoplastic resin film and a porous support made of thermoplastic resin fibers bonded to each other without substantially interposing an adhesive,
At least a portion of the fibers constituting the porous support form a web-like film made of a polymer constituting the fibers over a plurality of fibers, and the area ratio of the web-like film is 8%. ８０80%, and among the white spot defects on the printed matter obtained by performing solid black printing with a stencil printing machine, the number of white spot defects where the diameter of the minimum circumscribed circle of the white spot is 1 mm or more was 10 m ^2. Base paper for heat-sensitive stencil printing, characterized in that the number thereof is 100 or less. 2. The heat-sensitive stencil sheet according to claim 1, wherein the film and the porous support are made of polyester, and the fibers constituting the porous support are substantially long fibers. 3. The heat-sensitive stencil sheet according to claim 1, wherein the area ratio of the web-like film is 15 to 80%. 4. The number of white spot defects whose diameter of the minimum circumscribed circle of the white spot is 1 mm or more is 50 per 10 m ^{2 of} printing area.
2. The heat-sensitive stencil printing base paper according to claim 1, wherein the number is equal to or less than the number.