JPH09150496A - Heat sensitive stencil printing original paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain heat sensitive stencil printing original paper which is excellent in printing resistance by a method wherein water absorption of the original paper is made a specific % or under. SOLUTION: Heat sensitive stencil printing original paper is provided wherein in the heat sensitive stencil printing original paper composed of a thermoplastic resin film and a porous backing, water absorption of the original paper is 3% or under, preferably 2% or under, and further preferably 1.5% under. Since neither strength nor elastic modulus is lowered by moisture in the air and ink thereby, the original paper is neither deformed nor broken even though a great number of copies are printed. Therefore, strain or the like is not generated also in a printed image, and the original paper which is excellent in printing resistance can be obtained. Further, when the water absorption exceeds 3%, a drop of the strength and elastic modulus of the original paper is increased, and the printing resistance is deteriorated.

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. 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 acrylonitrile film, polyester film or vinylidene chloride film, and thin paper or natural and synthetic fibers made of natural fibers such as Manila hemp. There is known a structure in which a porous support composed of a thin paper or the like obtained by mixing and is bonded with an adhesive is used (for example, JP-A-57-18).
2495, JP-A-58-147396, JP-A-59-15898).

However, these conventional heat-sensitive stencil sheets are not always satisfactory in terms of printing durability. That is, when printing a large number of copies of 1000 sheets or more, there are drawbacks such as distortion of the printed image and tear of the base paper. There are various possible reasons for insufficient printing durability, one of which is due to the fibers constituting the support. In other words, the thin paper made of natural fibers, which has been used most often, has a rigidity as a support because the binder that bonds the fibers changes due to moisture contained in the printing ink or the fibers themselves swell. There is a drawback that the (elastic modulus) is lowered and the base paper is easily deformed. In addition, although the thin paper mainly composed of synthetic fibers reduces the swelling of the fibers themselves, the adhesive force between the fibers and the adhesive force between the film and the support may be reduced due to the moisture contained in the printing ink. Then, the rigidity of the support is impaired and the base paper is deformed.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned drawbacks and provide a heat sensitive stencil sheet having excellent printing durability.

[0005]

[Means for Solving the Problems] In order to achieve the above-mentioned object, the inventors of the present invention have conducted intensive studies by focusing on the running mechanism and the printing mechanism of a thermal stencil sheet in a printing machine, and as a result, specify the water absorption rate of the sheet. As a result, they have found that the drawbacks of conventional base paper can be improved, and have completed the present invention.

That is, the heat-sensitive stencil printing base paper of the present invention is
A heat-sensitive stencil printing base paper comprising a thermoplastic resin film and a porous support, wherein the water absorption of the base paper is 3% or less.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The base paper of the present invention has a water absorption of 3% or less, preferably 2% or less, more preferably 1.5%.
It is as follows. When the water absorption rate exceeds 3%, the strength and elastic modulus of the base paper are greatly reduced, and the printing durability is reduced.

The water absorption as referred to in the present invention means that the base paper is dipped in room temperature water (22 to 26 ° C.) for 2 hours, then taken out from the water and the adhering water is wiped off, then the temperature is 23 ° C. and the humidity is 65%. After being left for 15 minutes under water, the weight of the base paper is measured, and the difference from the weight of the base paper before water absorption is divided by the weight of the base paper before water absorption and expressed as a percentage.

Since the water absorption of the base paper of the present invention is specified, the strength and elastic modulus of the base paper will not be deteriorated by the water content in the air or the ink. Therefore, even if a large number of copies are printed, the base paper is deformed or torn. Never. Therefore, the base paper having excellent printing durability can be obtained without causing distortion or the like in the printed image.

In the base paper of the present invention, the retention ratio of the wet tensile elastic modulus in the vertical direction to the pre-wet tensile elastic modulus is preferably 50% or more, more preferably 60% or more, particularly preferably 70% or more. . When the retention rate is less than 50%, image distortion is likely to occur when printing a large number of copies.

The base paper of the present invention preferably has a wet tensile elastic modulus in the vertical direction of 0.1 kgf / cm or more, more preferably 0.14 kgf / cm or more, particularly preferably 0.18 kgf / cm or more. Is. When the wet tensile elastic modulus is less than 0.1 kgf / cm, printing durability is deteriorated, wrinkles are generated on the base paper, and printing clarity is deteriorated.

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.

Preferred examples of the polyester used for the polyester film include polyethylene terephthalate, copolymers of ethylene terephthalate and ethylene isophthalate, and copolymers of hexamethylene terephthalate and cyclohexane dimethylene terephthalate. 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 μm, and particularly preferably 0.1 to 3 μm.
m. 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.

The porous support in the present invention is not particularly limited as long as it has ink permeability such as conventionally known woven fabric, thin paper, papermaking paper, screen gauze, nonwoven fabric, etc., but in view of resistance to water absorption, Those mainly composed of synthetic fibers are preferable.

Examples of synthetic fibers include polyester,
Conventionally known materials such as polyamide, polyphenylene sulfide, polyacrylonitrile, polypropylene, polyethylene or copolymers 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 it is more preferable that at least 50% or more is polyester fibers.

Preferred polyesters include polyethylene terephthalate, polyethylene naphthalate, polycyclohexanedimethylene 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 in the present invention may be a paper making paper made from short fibers, a non-woven fabric or a woven fabric, a screen gauze or the like.
It may be a combination of these, but the fiber diameter,
A non-woven fabric is preferably used in terms of unit weight.

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 webs on a conveyor and forming 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 porous support in the present invention preferably has a mesh-like structure in which the fibers are irregularly fused to each other at the entanglement points. Particularly preferably, a thin film is formed on a part of the fused portion. That is, when the fibers of the support are made into a mesh-like body having a fused portion formed by forming a thin film, the strength of the support is stabilized and a uniform open pore form can be formed. The base paper can have a good balance between ink retention and permeability.

The support fibers preferably used in the present invention have an average diameter of usually 1 to 50 μm, preferably 1 to 3 μm.
It is 0 μm, more preferably 1 to 20 μm. If the average diameter is less than 1 μm, the strength of the support may be lowered, and if the average diameter is more than 50 μm, the smoothness may be lowered when the raw paper is used.

The basis weight of the support fibers in the present invention is usually preferably 1 to ²⁰ g / m ² , more preferably 2-1.
It is 5 g / m ² . If the basis weight exceeds 20 g / m ² ,
The transparency of the ink is lowered and the image clarity is lowered. If the basis weight is less than 1 g / m ² , sufficient strength as a support may not be obtained.

In the porous support of the present invention, when the support is observed two-dimensionally, the area fraction of the openings formed by the support is preferably 5 to 80%, more preferably 10 to 50%. Is. 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 base paper in the present invention is made by laminating and integrating the above thermoplastic resin film and the porous support. The method of integration is not particularly limited, and may be bonded using an adhesive under the condition that the perforation sensitivity of the film is not reduced, and the film and the support are directly heat-bonded without using the adhesive. Good. From the viewpoint of suppressing the water absorption of the base paper, it is more preferable to thermally bond the film and the support. The method of heat bonding is not particularly limited, but a method using a heating roll is particularly preferable from the viewpoint of processability.

The base paper according to the present invention may be produced by co-stretching an unstretched thermoplastic resin film and a porous support made of thermoplastic resin fibers having a low degree of orientation in a heat-bonded state. By co-stretching, the film and the porous support can be integrally stretched without peeling. At this time, the fibers of the support are stretched in a state of being fused to each other at the entanglement points, so that a mesh body suitable for the 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, the base paper of the present invention after biaxial stretching may be heat treated. The heat treatment temperature is not particularly limited and is appropriately determined depending on the type of thermoplastic resin used.

On the film side of the base paper of the present invention,
It is preferable to apply a release agent 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. Also, in the release agent,
Various additives such as antistatic agents, heat-resistant agents, antioxidants, organic particles, inorganic particles and pigments can be mixed and used together.

[0034]

[Characteristics measurement method]

(1) Water absorption rate (%) of base paper 10 cm x 10 cm after cutting the base paper with a single-edged razor
5 samples were collected. Put the sample in room temperature water 2
After soaking for a while, remove it from the water, lightly wipe off the water that adheres to the surface, and apply 1 at a temperature of 23 ° C and a humidity of 65%.
Leave for 5 minutes. Then, the weight of the base paper was measured, the water absorption rate was calculated from the weights before and after water absorption by the following equation, and an average value of n = 5 was obtained.

[(Weight of base paper after water absorption-weight of base paper before water absorption) / weight of base paper before water absorption] × 100

(2) Wet tensile modulus (kgf / cm) and retention rate (%) The base paper was cut in the vertical direction with a single-edged razor, and the width was 2c.
10 samples of m and 15 cm in length were collected. The sample was immersed in water at room temperature for 1 hour, then taken out from the water, water on the surface was lightly wiped off, and then the sample was immediately gripped by an air chuck of a tensile tester ("Tensilon" manufactured by Toyo Sokki Co., Ltd.). And the elastic modulus was measured. The measurement conditions were a chuck distance of 5 cm, a pulling speed of 5 cm / min, and a load-
Record the extension line (S-S curve) with a recorder (recorder speed 50c
m / min). From the initial rising slope of the SS curve, the tensile load at an elongation of 1% (elongation of 0.5 mm) is divided by the sample width to obtain the elastic modulus, and the number of samples is 1
The average value of 0 sheets was calculated.

Further, the tensile modulus before wetting was measured by the same procedure, and the retention rate was obtained from the following formula from the modulus before and after wetting.

Retention rate = (Elastic modulus after wetting / Elastic modulus before wetting)
× 100 (%)

(3) Evaluation of printability The prepared base paper is "Lisograph" G manufactured by Ideal Science Industry Co., Ltd.
It is supplied to R275 and the thermal head plate making method is used.
A plate having a character size of 6 to 10.5 and a circle (painted in black with a circle) having a diameter of 0.5 to 15 mm was used as an original plate. Then, 1000 prints were printed, and the printability and printing durability were evaluated as follows.

[Printability] The printed matter was visually evaluated as follows. Clear prints with no distortion ○, clear prints with slight distortion △
Those with significant distortion were marked with x.

[Printing durability] The length in the lengthwise direction of the base paper after printing 1000 sheets was measured, and the amount of change from the original length was expressed as an elongation percentage (%), and evaluated according to the following criteria. 0.5% elongation
Less than ◯, 0.5 to 1.0% of less △, 1.0
Those that exceeded% were defined as x.

The evaluation results are shown in Table 1.

[0043]

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

Example 1 A polyethylene terephthalate raw material ([η] = 0.58, Tm = 255 ° C.) was spun by a melt-blowing method at a die temperature of 285 ° C. using a rectangular die having a hole diameter of 0.3 mm and 80 holes. Take out, disperse and collect fibers on the conveyor, and have a basis weight 1.
A nonwoven fabric of 00 g / m ² was prepared.

Then, polyethylene terephthalate 87
Copolyester resin raw material ([η] = 0.64, T
m = 212 ° C.) using an extruder, the temperature of the T-die base is 27
It was extruded at 5 ° C and cast on a cooling drum to prepare an unstretched film.

The above nonwoven fabric was laid on the unstretched film, supplied to a heating roll and thermally bonded at a roll temperature of 80 ° C. to prepare a laminated sheet.

The laminated sheet was placed between heating rolls at 93 ° C.
After stretching 3.5 times in the length direction, it was fed into a tenter type stretching machine, stretched 4.2 times in the width direction at 90 ° C., and further heat-treated at 130 ° C. inside the tenter to produce the base paper of the present invention. .

The basis weight of the support fiber of the obtained base paper is 6.8.
g / m ^2, the average diameter of the support fibers was 3.8 .mu.m. The thickness of the film was 1.0 μm. The water absorption of the base paper was 0.7%.

Example 2 A polyethylene terephthalate raw material ([η] was used at a die temperature of 275 ° C. using a die having a hole diameter of 0.25 mm and 90 holes.
= 0.64, Tm = 256 ° C.) was spun out and dispersed and collected on a conveyor by an air ejector at a spinning speed of 1000 m / min to prepare a nonwoven fabric having a fiber basis weight of 120 g / m ² .

Then, polyethylene terephthalate 80
Copolyester resin raw material consisting of mol% and polyethylene isophthalate 20 mol% ([η] = 0.6, Tm
= 199 ° C.) using an extruder, the temperature of the T-die base is 285
It was extruded at ℃ and cast on a cooling drum to prepare an unstretched film.

The non-woven fabric was placed on the unstretched film, supplied to a heating roll and thermally bonded at a roll temperature of 85 ° C. to prepare a laminated sheet.

The laminated sheet was stretched 3.0 times in the length direction with a heating roll at 87 ° C., then fed into a tenter type stretching machine, and stretched 3.3 times in the width direction at 93 ° C. Further, the base paper of the present invention was produced by heat treatment at 160 ° C. inside the tenter.

The basis weight of the support fiber of the obtained base paper is 12.
The average diameter of the support fibers was 4 g / m ² , and the average diameter was 5.3 μm. The film thickness was 1.6 μm. The water absorption of the base paper was 0.9%.

Example 3 The non-woven fabric prepared in Example 1 was stretched 4 times in the length and width with a film stretcher to give a fabric weight of 6 g / m ² and an average fiber diameter of 3.8 μ.
m porous support was prepared.

Then, the thickness produced in Example 1 was 1.0 μm.
The film of m was attached to the above support with a polyester adhesive to prepare a base paper of the present invention. The water absorption of the base paper was 1.2%.

Example 4 40 parts of Manila hemp and 60 parts of polyester fiber having an average fiber diameter of 10 μm and a length of 10 mm were mixed to prepare a porous support having a basis weight of 11 g / m ^{2 with} a Fourdrinier paper machine.

Then, the thickness produced in Example 2 was 1.6 μm.
The film of m was attached to the above support with a polyester adhesive to prepare a base paper of the present invention. The water absorption of the base paper was 2.7%.

Comparative Example 1 100% natural fiber made from Manila hemp as a raw material, and a unit weight of 9.8 g.
/ M ² thin paper and a 1.7 μm-thick polyester film were laminated using a vinyl acetate adhesive to prepare a printing base paper. The water absorption of the base paper was 5.0%.

Comparative Example 2 60 parts of Manila hemp and 40 parts of polyester fibers having an average fiber diameter of 10 μm and a length of 10 mm were mixed to prepare a porous support having a basis weight of 12 g / m ^{2 with} a Fourdrinier paper machine.

Then, the thickness of 1.6 μm produced in Example 2 was used.
The film of m was attached to the above support with a polyester adhesive to prepare a base paper for printing. The water absorption of the base paper was 3.6%.

[0061]

[Table 1] As can be seen from the results in Table 1, the heat-sensitive stencil printing base paper of the present invention having a water absorption of the base paper of 3% or less has excellent printing durability.

[0062]

EFFECTS OF THE INVENTION Since the heat-sensitive stencil printing base paper of the present invention specifies the water absorption rate of the base paper, the strength and elastic modulus do not decrease due to moisture in the printing ink, and the base paper can be printed even if a large number of sheets are printed. Does not deform. Therefore, the printed image is not distorted and the printing durability is excellent.

Claims (3)

[Claims] 1. A base paper for heat-sensitive stencil printing comprising a thermoplastic resin film and a porous support, wherein the water absorption of the base paper is 3% or less. 2. The base paper for heat-sensitive stencil printing according to claim 1, wherein the thermoplastic resin film is a polyester resin film. 3. The base paper for heat-sensitive stencil printing according to claim 1, wherein the porous support is mainly composed of polyester resin fibers.