JPH0867080A - Thermosensitive stencil printing sheet - Google Patents

Abstract

PURPOSE: To obtain a stencil printing sheet which produces a sharply printed image and demonstrates superb running and anti-crease properties by specifying tensile strength and bending rigidity, i.e. the strength and resiliency of the sheet. CONSTITUTION: This thermosensitive stencil printing sheet is composed of thermoplastic resin film and a porous support consisting mainly of synthetic fiber laminated together. In addition, the tensile strength of the sheet in a vertical direction is, at least, 0.3kgf/cm and the bending rigidity B value in a vertical or a horizontal direction is, at least, 0.02gf.cm<2> /cm.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a heat-sensitive stencil printing base paper. More specifically, the present invention relates to a heat-sensitive stencil printing base paper which is punched by a halogen lamp, a xenon lamp, a flash bulb or the like for flash or infrared irradiation, pulsed irradiation with a laser beam or the like, or a thermal head.

[0002]

2. Description of the Related Art Conventional base papers used for heat-sensitive stencil printing include thermoplastic resin films such as polyester film, vinylidene chloride film, or polypropylene film, and thin paper, non-woven fabric, screen gauze made of natural fibers or synthetic fibers. There is known a structure in which the constituted porous support is bonded with an adhesive (JP-A-57-182495 and JP-A-58-14).
7396, JP-A-59-15898, etc.).

However, these conventional heat-sensitive stencil sheets are not always satisfactory in terms of the sharpness of printed images. There are various possible reasons for insufficient image clarity, one of which is due to the fibers constituting the support. That is, since the thin paper made of natural fibers that has been used most often conventionally is thick and uneven, and is flat, the ink transmission tends to be uneven, and in particular, it exists in the perforated portion of the film. The fibers impede the ink transmission, and there are drawbacks such as faint printing and white spots in solid printing.

In order to improve these drawbacks, papermaking paper or non-woven fabric mainly made of synthetic fiber such as polyester fiber or polypropylene fiber is used in place of thin paper made of natural fiber to thin the fiber of the support or Measures such as reducing the weight per unit area as much as possible have been taken (JP-A-59-2896, JP-A-59-16793, JP-A-2-67197, etc.).

Further, in order to improve the printability, it is effective to improve the perforation sensitivity of the thermoplastic resin film. Therefore, the thickness of the film is specified and a base paper for heat-sensitive stencil which is made as thin as possible is proposed. There is.

However, although the image clarity is improved by thinning the fibers of the support, reducing the weight per unit area, and reducing the thickness of the film, the runnability of the base paper is reduced and printing is performed. There are drawbacks such that clogging occurs in the machine and wrinkles occur when the perforated base paper is wound around the printing drum, and the wrinkles deteriorate the printing quality.

[0007]

SUMMARY OF THE INVENTION The present invention is intended to solve the above-mentioned drawbacks and to provide a heat-sensitive stencil sheet having excellent image clarity, running property and operability.

[0008]

[Means for Solving the Problems] In order to achieve the above-mentioned object, the inventors of the present invention have conducted diligent research by paying attention to a running mechanism and a printing mechanism of a thermal stencil sheet (hereinafter referred to as a sheet) in a printing machine. The inventors have found that the defects of conventional base paper can be improved by specifying the tensile strength and bending rigidity, and have completed the present invention.

That is, the present invention is a base paper for heat-sensitive stencil which is obtained by laminating a thermoplastic resin film and a porous support mainly composed of synthetic fibers, and the tensile strength of the base paper in the vertical direction is 0.3 kgf / cm or more, vertical or horizontal K
An ES type flexural rigidity B value is 0.02 gf · cm ² / cm or more, which is a heat-sensitive stencil sheet.

The thermoplastic resin film in the present invention is
For example, conventionally known materials such as polyester, polyamide, polypropylene, polyethylene, polyvinyl chloride, polyvinylidene chloride or copolymers thereof are used, and polyester film is particularly preferably used from the viewpoint of perforation sensitivity.

The polyester used for the polyester film is preferably polyethylene terephthalate, a copolymer of ethylene terephthalate and ethylene isophthalate, a copolymer of hexamethylene terephthalate and cyclohexane dimethylene terephthalate, and the like. Particularly preferred for improving the perforation sensitivity are a copolymer of ethylene terephthalate and ethylene isophthalate, a copolymer of hexamethylene terephthalate and cyclohexane dimethylene terephthalate, and the like.

The thermoplastic resin film in the present invention is
Usually, it is preferably stretched, and can be produced by a conventionally known T-die method, inflation method, or the like. For example, in the T-die method, an unstretched film can be produced by extruding a polymer on a cast drum, then longitudinally stretched by a heating roll group, and if necessary, supplied to a tenter or the like for lateral stretching. The thickness of the unstretched film can be adjusted by adjusting the slit width of the die, the discharge amount of the polymer, and the rotation speed of the cast drum.Also, the rotation speed of the heating roll group and the setting of the tenter can be adjusted. By changing the width, it is possible to stretch at a desired stretching ratio.

In the thermoplastic resin film of the present invention, if necessary, an organic lubricant such as a flame retardant, a heat stabilizer, an antioxidant, an ultraviolet absorber, an antistatic agent, a pigment, a dye, a fatty acid ester, a wax, or a polysulfate. An antifoaming agent such as siloxane can be blended.

Further, slipperiness can be imparted if necessary. The method for imparting slipperiness is not particularly limited, but examples thereof include clay, mica, titanium oxide, calcium carbonate, kaolin, talc, inorganic particles such as wet or dry silica, organic particles containing acrylic acid, styrene and the like as constituent components. And the like, a method using internal particles, a method of applying a surfactant, and the like.

The thickness of the thermoplastic resin film in the present invention is usually preferably 0.1 to 10 μm, more preferably 0.1 to 5.0 μm, and more preferably 0.1.
Is about 3.0 μm. If the thickness exceeds 10 μm, the piercing property may decrease, and if it is less than 0.1 μm, the film forming stability may deteriorate.

As the synthetic fiber in the present invention, a conventionally known one such as polyester, polyamide, polyphenylene sulfide, polyacrylonitrile, polypropylene, polyethylene or a copolymer thereof can be used. These synthetic fibers may be used alone or in combination of two or more, and may also include natural fibers and regenerated fibers. In the present invention, polyester fibers are particularly preferably used from the viewpoint of thermal stability during perforation, and at least 60%
More preferably, the above is a polyester fiber.

Preferred polyesters include polyethylene terephthalate, polyethylene naphthalate, polycyclohexane dimethylene terephthalate, and copolymers of ethylene terephthalate and ethylene isophthalate. From the viewpoint of thermal dimensional stability during perforation, polyethylene terephthalate and polyethylene naphthalate are particularly preferable. If necessary, these polymers may include flame retardants, heat stabilizers, antioxidants, UV absorbers, antistatic agents, organic lubricants such as pigments, dyes, fatty acid esters and waxes, or defoaming agents such as polysiloxanes. It can be blended.

The porous support composed mainly of synthetic fibers in the present invention has the following properties when the support is observed two-dimensionally.
The area fraction of the openings formed by the support is preferably 5-8.
It is 0%, more preferably 10 to 50%. If the open area fraction is less than 5%, the ink permeability is poor, and the printed image becomes faint and the sharpness deteriorates. If it exceeds 80%, the ink holding property is lowered, so that the printed image becomes bleeding and the show-through easily occurs. The open area ratio in the present invention is a percentage of the area occupied by the open area when a certain area of the support is observed in a plane.

The porous support in the present invention preferably forms a mesh-like body in which fibers are irregularly fused to each other at the entanglement points. Particularly preferably, a thin film-like fold is formed in a part of the fusion-bonded portion. That is, the fibers of the support can be formed into a mesh-like body having a fused portion formed by forming a thin film fold, so that the strength of the support can be stabilized and a uniform opening shape can be formed. It is possible to obtain a base paper having a good balance between printing ink retention and transparency.

The fiber basis weight of the porous support in the present invention is usually preferably ^{2 to 20} g / m ² , and more preferably 5 to 15 g / m ² . If the weight per unit area exceeds 20 g / m ² , the ink permeability decreases and the image clarity decreases. If the basis weight is less than 2 g / m ² , sufficient strength as a support may not be obtained.

The porous support made of synthetic fiber in the present invention may be a papermaking paper made from short fibers, a non-woven fabric or a woven fabric, a screen gauze or the like. Nonwoven fabric is more preferably used.

The non-woven fabric can be produced by a conventionally known direct melt spinning method such as a flash spinning method, a melt blow spinning method, and a spun bond spinning method. For example, in the melt blow spinning method, when the molten polymer is discharged from the spinneret, hot air is blown from the periphery of the spinneret, the discharged polymer is made finer in fineness, and then sprayed on a net conveyor arranged at an appropriate position. It is manufactured by collecting and collecting a web to form a web.

Similarly, in the spunbond method, the polymer discharged from the die is pulled by an air ejector, and the obtained filament is collided with a collision plate to open the fiber,
It is manufactured by collecting it on a conveyor to form a web. The basis weight of the web can be arbitrarily set by appropriately setting the polymer discharge amount and the conveyor speed.

In the porous support of the present invention, the surface of the fiber constituting the ink is optionally subjected to chemical treatment with acid, alkali or the like, corona treatment, low temperature plasma treatment or the like in order to impart affinity with the ink. Good.

The base paper in the present invention is made by laminating and integrating the above-mentioned thermoplastic resin film and a porous support mainly composed of synthetic fibers. The lamination may be carried out by using an adhesive under the condition that the perforation sensitivity of the film is not lowered, or the film and the support may be thermally bonded without using the adhesive. From the viewpoint of printing clarity, it is preferable to directly fix the thermoplastic resin film and the porous support by heat bonding without using an adhesive.

Thermal bonding is usually carried out by thermocompression bonding in which the thermoplastic resin film and the porous support are directly bonded while heating. The method of thermocompression bonding is not particularly limited, but thermocompression bonding with a heating roll is particularly preferable from the viewpoint of processability.

In the present invention, it is particularly preferable to co-stretch the unstretched thermoplastic resin film and the low-orientation porous support in a thermocompression-bonded state. By co-stretching, the film and the porous support can be suitably stretched integrally without peeling. At this time, since the fibers of the support are stretched in a state of being fused to each other at the entanglement point,
A reticulate body suitable as a support can be formed. Further, by co-stretching the both together, the thermoplastic resin film and the porous support are directly fixed and integrated without using an adhesive.

The method of co-stretching is not particularly limited, but biaxial stretching is usually preferred. The biaxial stretching may be either sequential biaxial stretching or simultaneous biaxial stretching. In the case of sequential biaxial stretching, it is general to stretch in the longitudinal direction and then in the transverse direction, but the stretching may be reversed. The stretching ratio is not particularly limited and is appropriately determined depending on the type of thermoplastic resin used, the perforation sensitivity required for the base paper, and the like, but normally 2 to 8 times in both the length and width are suitable. Further, after biaxial stretching, it may be re-stretched longitudinally or laterally or simultaneously in longitudinal and lateral directions.

Further, it is preferable to heat-treat the base paper of the present invention after biaxial stretching. The heat treatment temperature is not particularly limited and is appropriately determined depending on the type of thermoplastic resin used.

The base paper of the present invention has a tensile strength in the vertical direction of 0.3 kgf / cm or more, and a KE in the vertical or horizontal direction.
The S-type flexural rigidity B value is 0.02 gf · cm ² / cm or more. Here, the vertical direction is a running direction when the base paper is supplied to the printing machine, and the horizontal direction is a direction perpendicular to the running direction. Further, the KES formula referred to in the present invention means KAWABATA'S.
EVALUATION SYSTEM FOR FAB
RICS is an abbreviation for RICS and is a method widely adopted as a physical quantity measuring method for texture of woven and knitted fabrics, which was devised by Professor Toshio Kawabata of Kyoto University.

Here, the mechanism of the stencil printing machine will be described. First, when you set the print document on the reading section of the printing machine,
The reading sensor reads the light and shade corresponding to the figures and characters of the original as a digital signal and sends the signal to the thermal head. On the other hand, the base paper set in the holder is sent to a thermal head portion by a feed roll and punched by heating the thermal head. The master paper, which has been plate-prepared, has its leading end gripped and wound around a printing drum. Ink is pushed out from the inside of the printing drum, transferred to the printing paper through the perforated portion of the master, and printing is completed.
The printing paper is supplied in synchronization with the rotation of the printing drum, and the required number of sheets can be continuously printed.

As described above, tension is applied to the base paper in the running direction in the printing machine. If the tensile strength of the base paper in the vertical direction is less than 0.3 kgf / cm, not only the strength of the base paper will be insufficient to prevent smooth running, but also the base paper will be torn in extreme cases.

Also, the vertical or horizontal KE of the base paper
If the S-type flexural rigidity B value is less than 0.02 gf · cm ² / cm, the so-called stiffness is insufficient, and worm-like wrinkles occur when the base paper is wound around the printing drum.
In the wrinkle portion, the image is distorted or the ink is faded, resulting in a print defect. That is, in order to satisfy the running property and the wrinkle resistance of the base paper, it is essential to simultaneously satisfy the tensile strength and the bending rigidity (strength of the waist) of the base paper.

The peel strength between the thermoplastic resin film constituting the base paper of the present invention and the porous support is preferably 1 g / 25.
mm or more, more preferably 3 g / 25 mm or more, and further preferably 5 g / 25 mm or more. Peel strength is 1g
If it is smaller than / 25 mm, the thermoplastic resin and the porous support may be separated from each other when the base paper is fed and conveyed to the printing machine.

A release agent is preferably applied to the film surface of the base paper of the present invention to prevent sticking during punching. As the release agent, a conventionally known release agent such as silicone oil, silicone resin, fluorine resin, and surfactant can be used.

Further, various additives such as an antistatic agent, a heat-resistant agent, an antioxidant, an organic particle, an inorganic particle and a pigment can be mixed and used in the release agent.

[0037]

[Characteristics measurement method]

(1) Tensile strength (kgf / cm) The base paper is cut in the vertical direction with a single-edged razor, and the width is 2c.
10 samples of m and 15 cm in length were collected. The sample was pulled with a "Tensilon" tensile tester (manufactured by Toyo Sokki Co., Ltd.) at a test speed of 5 cm / min until breaking, the maximum load was divided by the sample width to determine the strength, and the average strength of 10 samples was determined. . The test length was 5 cm.

(2) KES type flexural rigidity B value It was measured using a pure bending tester (KES-F2) manufactured by Kato Iron Works Co., Ltd. The sample is held by a chuck having a length of 20 cm and a width of 1 cm, and the curvature K = −2.5 to +2.5 (c
Pure bending with constant velocity curvature was performed in the range of m ⁻¹ ). The deformation rate was 0.5 cm ⁻¹ / sec. The relationship between the bending moment (M: gf · cm / cm) and the curvature (K: cm ⁻¹ ) per unit length of the sample was plotted to obtain an MK curve. A slope (Bf) between curvatures 0.5 and 1.5 and -0.
The absolute value (Bb) of the inclination between 5 and -1.5 was measured, and the bending rigidity B value (gf · cm ² / cm) per unit length was calculated by the following formula.

B = (Bf + Bb) / 2

(3) Evaluation of printability The prepared base paper is "Lisograph" R manufactured by Ideal Science Co., Ltd.
It was supplied to A205, and a thermal head type plate making method was used to make a plate having a character size of 6 to 10.5 and a (circle filled in black) of 0.5 to 15 mmφ as an original. . By visually deciding what was printed using a plate-making manuscript, the letters are clear and there are no white spots on the solid black areas, and the letters are unclear and the black solid portions are marked with white areas. It was evaluated as Δ when it was in the middle of the above range and was practically manageable.

(4) Evaluation of Runnability and Wrinkle Resistance Runnability: The one in which the base paper smoothly ran was evaluated as ◯, and the one in which the base paper jam occurred was evaluated as x.

Wrinkle resistance: The case where no wrinkles were formed on the printing drum was marked with ◯, and the case where wrinkles were formed was marked with x.

[0043]

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited thereto.

Example 1 Using a rectangular die having a hole diameter of 0.35 mm and 80 holes, a polyethylene terephthalate raw material ([η] = 0.61, Tm = 257 ° C.) was spun by a melt blow method at a die temperature of 285 ° C. Take out, disperse and collect fibers on the conveyor, and fabric weight 6
Nonwoven fabrics of 0, 80 and 100 g / m ² were prepared. The crystallinity of the nonwoven fabric was 6%.

Then, polyethylene terephthalate 85
Copolyester resin raw material ([η] = 0.65, T
m = 210 ° C.) is extruded at a T-die die temperature of 270 ° C. using an extruder with a screw diameter of 40 mm, and the diameter is 300 mm.
An unstretched film was produced by casting on a cooling drum of

On the unstretched film, a basis weight of 80 g / m ²
The non-woven fabric is piled up and supplied to a heating roll to obtain a roll temperature of 80
Thermocompression bonding was performed at 0 ° C. to produce a laminated sheet.

The laminated sheet was placed between heating rolls at 90 ° C.
After stretching 3.5 times in the length direction, it was fed into a tenter type stretching machine, stretched 4 times in the width direction at 95 ° C., and further heat treated at 200 ° C. inside the tenter. A wax release agent was applied to the film surface at the inlet of the tenter with a gravure coater to give a dry weight of 0.1 g / m ² to prepare a heat-sensitive stencil sheet.

The fiber basis weight of the obtained base paper was 5.7 g / m.
^{2. The} film thickness was 1.9 μm. Further, the tensile strength of the base paper in the vertical direction is 0.36 kgf / cm, KES
Bending stiffness B value is vertical / horizontal = 0.025 / 0.023
It was gf · cm ² / cm.

Example 2 Using the nonwoven fabric having a basis weight of 100 g / m ² prepared in Example 1, a heat sensitive stencil sheet was prepared in the same manner as in Example 1. The fiber basis weight of the base paper was 7.2 g / m ² , and the film thickness was 1.
It was 8 μm. The tensile strength of the base paper in the vertical direction is 0.48 kgf / cm, and the KES flexural rigidity B value is vertical /
The width was 0.028 / 0.025 gf · cm ² / cm.

Example 3 A polyethylene terephthalate raw material ([η] =) was used at a die temperature of 285 ° C. using a die having a hole diameter of 0.3 mm and 70 holes.
0.63, Tm = 258 ° C.) was spun out and dispersed and collected on a conveyer by an air ejector at a spinning speed of 1600 m / min to prepare a nonwoven fabric having a fiber areal weight of 40, 60, 80 g / m ² . The crystallinity of the nonwoven fabric was 8%.

Then, polyethylene terephthalate 75
Copolyester resin raw material ([η] = 0.65, T
m = 198 ° C.) is extruded at a T-die die temperature of 280 ° C. using an extruder with a screw diameter of 40 mm, and the diameter is 300 mm.
An unstretched film was produced by casting on a cooling drum of

On the unstretched film, the above basis weight is 60 g.
/ M ² of non-woven fabrics were stacked, supplied to a heating roll, and thermocompression bonded at a roll temperature of 85 ° C. to produce a laminated sheet.

The laminated sheet was stretched 3 times in the length direction with a heating roll at 95 ° C., and then fed into a tenter type stretching machine,
The film was stretched 3.3 times in the width direction at 100 ° C. Furthermore, it heat-processed at 200 degreeC inside a tenter. In addition, at the inlet of the tenter, a wax-based release agent was applied to the film surface by a gravure coater with a dry weight of 0.1 g / m ² .
The fiber basis weight of the obtained base paper was 6.1 g / m ² , and the film thickness was 2.1 μm. In addition, the tensile strength of the base paper in the vertical direction is 0.51 kgf / cm, and the KES flexural rigidity B is
The value is vertical / horizontal = 0.041 / 0.027 gf · cm ²
Was / cm.

Example 4 Using the nonwoven fabric having a basis weight of 80 g / m ² prepared in Example 3, a heat sensitive stencil sheet was prepared in the same manner as in Example 3. The fiber basis weight of the base paper was 8.1 g / m ² , and the film thickness was 2.
It was 0 μm. In addition, the tensile strength of the base paper in the vertical direction is 0.80 kgf / cm, and the KES flexural rigidity B value is vertical /
Width = 0.052 / 0.029 gf · cm ² / cm.

Comparative Example 1 A heat-sensitive stencil sheet was produced under the same conditions as in Example 1 except that the nonwoven fabric having a basis weight of 40 g / m ² produced in Example 1 was used and the stretching ratio in the width direction was set to 3. . The basis weight of the base paper was 3.8 g / m ² , and the film thickness was 2.2 μm. The tensile strength of the base paper in the vertical direction is 0.25 kg.
f / cm, KES type flexural rigidity B value is vertical / horizontal = 0.0
It was 14 / 0.008 gf · cm ² / cm.

Comparative Example 2 Using the non-woven fabric having a basis weight of 60 g / m ² produced in Example 1, except that the stretching ratio in the length direction was 3.7 times and the stretching ratio in the width direction was 3.5 times. A base paper for heat-sensitive stencil was prepared under the same conditions as in Example 1. The basis weight of the base paper is 4.5 g /
The film thickness was m ² and the film thickness was 1.8 μm. The tensile strength of the base paper in the vertical direction is 0.28 kgf / cm, KES
Formula Bending rigidity B value is vertical / horizontal = 0.025 / 0.021
It was gf · cm ² / cm.

Comparative Example 3 Heat-sensitive under the same conditions as in Example 3 except that the nonwoven fabric having a basis weight of 40 g / m ² produced in Example 3 was used and the draw ratio in the length direction and the width direction was 3.5 times. A stencil sheet was prepared. The fiber basis weight of the base paper was 3.3 g / m ² , and the film thickness was 1.8 μm. Further, the tensile strength of the base paper in the vertical direction is 0.33 kgf / cm, and the BES value of KES type bending rigidity is vertical / horizontal = 0.018 / 0.016 gf · cm ² / c.
It was m.

[0058]

[Table 1] As can be seen from the results in Table 1, the tensile strength of the base paper in the vertical direction is 0.3 kgf / cm or more, and the KES flexural rigidity B value in the vertical or horizontal direction is 0.02 gf · cm ² /
The base paper for heat-sensitive stencil of the present invention having a size of not less than cm has good printability and excellent running property and wrinkle resistance.

[0059]

INDUSTRIAL APPLICABILITY In the heat-sensitive stencil sheet of the present invention, the tensile strength and bending rigidity, that is, the strength of the sheet and the stiffness of the sheet are specified, so that the printed image is excellent in sharpness, and the running property and wrinkle resistance are excellent. An excellent base paper can be obtained.

Claims (3)

[Claims] 1. A base paper for heat-sensitive stencil, comprising a thermoplastic resin film and a porous support mainly composed of synthetic fibers, which has a tensile strength of 0.3 kgf /
A stencil sheet for heat-sensitive stencil printing, characterized by having a BES value of KES type bending rigidity in the vertical direction or the horizontal direction of 0.02 gf · cm ² / cm or more. 2. The base paper for heat-sensitive stencil according to claim 1, wherein the thermoplastic resin film is a polyester resin film. 3. The heat-sensitive stencil sheet according to claim 1, wherein the synthetic fiber is mainly made of polyester resin.