JP2000318336A - Heat-sensitive stencil printing base paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a base paper of superior image sharpness and printability not generating creases even when a number of sheets are printed by setting the ratio between the penetrating microwave strength in parallel with the longitudinal direction of the base paper and the penetrating microwave strength in parallel with the width direction in a specified range. SOLUTION: A base paper to be used has a constitution in which both of penetrating microwave strength Mx in parallel with the longitudinal direction of the base paper and the penetrating microwave strength My in parallel with the width direction satisfy the formula 1.0<My/Mx<=2.0. As a material for a thermoplastic film, preferably a polyester and its copolymer or a blend are used. Also it is most preferable to use a porous substrate composed of thermoplastic fibers using a polyester from the viewpoints of spinning properties and strong extension ratio characteristics and the like. The weight per unit area of the porous substrate is preferably set as 2-20 g/m2, and birefringence is set as 0.05 or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stencil sheet for heat-sensitive stencil printing which is perforated by a pulsed irradiation of a thermal head or a laser beam or the like. Image clarity,
The present invention relates to a heat-sensitive stencil sheet having excellent printability.

[0002]

2. Description of the Related Art Thermosensitive stencil printing is a method in which a thermoplastic resin film is bonded to an ink-permeable porous support as a stencil sheet for heat-sensitive stencil printing. Plate making,
The printing ink is leached into the perforated portion from the porous support side and printed on printing paper. In recent years, heat-sensitive stencil printing machines have been improved to meet the demands for high-definition printing and high-speed plate making, such as increasing the dot density of the thermal head and reducing the energy required for plate making. Base paper is required. At this time, it is desired to simultaneously obtain good transportability of the base paper and printability such that there are few white spots (white printing defects occurring in black solid portions of the printed matter). Conventionally, as heat-sensitive stencil printing base paper, a polyester film, a vinyl resin film such as a vinylidene chloride-based film, a natural resin, a synthetic fiber or a synthetic fiber or a thin paper, a nonwoven fabric, a gauze or the like obtained by mixing these fibers, etc. A structure in which a support is bonded with an adhesive is known (for example, JP-A-51-2513 and JP-A-57-182495).

However, these heat-sensitive stencil sheets have not always been satisfactory in terms of the sharpness of the printed image. There are various possible reasons, one of which is attributed to the fibers constituting the support.
That is, the thin paper used conventionally has thick and uneven fibers and is flat, so that the ink permeability tends to be non-uniform. There were drawbacks, such as hindered printing and fading of white spots in solid printing.

[0004] In order to improve these drawbacks, instead of using thin paper made of natural fibers, paper fibers or nonwoven fabrics mainly composed of synthetic fibers such as polyester fibers or polypropylene fibers are used to reduce the thickness of the fibers of the support or to reduce the fibers. Measures such as minimizing the weight per unit area have been taken (Japanese Patent Laid-Open No.
9-2896, JP-A-59-16793,
JP-A-2-67197). In addition, to improve the printability, it is effective to improve the perforation sensitivity of the thermoplastic resin film, therefore, by specifying the thickness of the film,
A heat-sensitive stencil sheet as thin as possible has been proposed.

[0005] However, by making the fibers of the support thinner, reducing the basis weight, and reducing the thickness of the film, the image clarity is improved, but the strength of the base paper is reduced and a large number of sheets are required. When printing is performed, wrinkles are partially generated on the base paper on the plate cylinder, and there is a problem that printing quality is deteriorated due to printing defects caused by the wrinkles.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide a heat-sensitive stencil sheet having excellent image clarity and printability.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, the present invention provides a heat-sensitive stencil printing paper comprising a thermoplastic film and a porous support made of thermoplastic fibers, which is parallel to the longitudinal direction of the paper. The heat-sensitive stencil printing paper is characterized in that the transmitted microwave intensity Mx and the transmitted microwave intensity My parallel to the width direction satisfy the following expression (1).

1.0 <My / Mx ≦ 2.0 (1)

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have conducted intensive studies on a method for preventing a decrease in print quality while improving image clarity. By reducing the basis weight of the porous support or reducing the thickness of the film, the image clarity can be improved, but the printing quality is liable to deteriorate due to printing defects due to wrinkles of the base paper. In particular, since the base paper is obtained by laminating a thermoplastic film and a porous support, it has not been easy to develop a thermoplastic film and a porous support, respectively, and to examine a combination of both.

As a result of studies, the inventors have found that printing defects and white spots due to wrinkles when printing a large number of sheets are caused by the transmitted microwave intensity Mx parallel to the longitudinal direction of the base paper and the transmitted microwave intensity parallel to the width direction of the base paper. It was found that it was affected by the ratio with My. That is, the present invention provides a heat-sensitive stencil printing paper comprising a thermoplastic film and a porous support made of thermoplastic fiber, and particularly, by using a base paper having a My / Mx satisfying the above-mentioned formula (1), Even with a small amount of base paper, there is no problem of the above-mentioned disadvantages, image clarity,
It has been found that a printed matter having excellent printability can be obtained.

In the base paper for heat-sensitive stencil printing of the present invention, M
When y / Mx is 1 or less, printing defects due to wrinkles occur when printing a large number of sheets.

A more preferable range of My / Mx is as follows:
This is the range represented by the following equation (2).

1.2 ≦ My / Mx ≦ 2.0 (2) By satisfying the expression (2), there is almost no change in dimensional accuracy when printing is further repeated. According to various findings by the present inventors, the upper limit of My / Mx in the preferred heat-sensitive stencil sheet of the present invention is up to 2.0. If the My / Mx value exceeds 2.0, plate wrinkles (wrinkles generated when printing on a printing drum) occur, which causes printing defects and lowers print quality.

The thermoplastic film used in the present invention includes polyester, polyamide, polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, and the like.
Each copolymer, a blend thereof and the like can be mentioned, and preferably, polyester and its copolymer or blend are used.

In the present invention, the polyester used for the polyester film is a polyester containing an aromatic dicarboxylic acid or an aliphatic dicarboxylic acid and a diol as main components. Here, as the aromatic dicarboxylic acid, for example, terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid,
4,4'-biphenyldicarboxylic acid, 4,4'-biphenyletherdicarboxylic acid, 4,4'-biphenylsulfonedicarboxylic acid, and the like can be used. Among them, terephthalic acid, isophthalic acid, and 2,6-naphthalenedicarboxylic acid can be preferably used. As the aliphatic dicarboxylic acid component, for example, adipic acid, suberic acid,
Sebacic acid, dodecanedioic acid and the like can be used. One of these acid components may be used alone, or two or more thereof may be used in combination. Further, an oxyacid such as hydroxybenzoic acid may be partially copolymerized. Examples of the diol component include ethylene glycol, 1,2-propanediol, 1,3-propanediol, neopentyl glycol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, , 6-hexanediol, 1,2-cyclohexanedimethanol, 1,
3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, diethylene glycol, triethylene glycol, polyalkylene glycol, 2,2'-
Bis (4'-β-hydroxyethoxyphenyl) propane or the like can be used. Among them, ethylene glycol, 1,4-butanediol and 1,6-hexanediol are preferably used. These diol components may be used alone or in combination of two or more.

The polyester used for the polyester film in the present invention is preferably polyethylene terephthalate, a copolymer of ethylene terephthalate and ethylene isophthalate, a copolymer of ethylene terephthalate and ethylene naphthalate, hexamethylene terephthalate and cyclohexane dimethylene. Copolymers with terephthalate, blends of polyethylene terephthalate and polybutylene terephthalate, and the like can be given. Particularly preferred from the viewpoints of perforation sensitivity and stretchability are copolymers of ethylene terephthalate and ethylene isophthalate, and copolymers of ethylene terephthalate and ethylene naphthalate.

In the present invention, the thickness of the film is preferably from 0.1 to 3 μm, more preferably from 0.2 to 2.5 μm, particularly preferably from 0.3 to 3 μm, from the viewpoint of sensitivity and film formation stability.
2.2 μm. The crystal melting energy (ΔHu) of the film is preferably 5 to 50 J / g, more preferably 10 to 50 J / g, and particularly preferably 15 to 50 J / g.
/ G. If ΔHu is 5 to 50 J / g, the variation in perforation sensitivity of the film is small.

The thermoplastic fibers constituting the porous support in the present invention are made of a spinnable thermoplastic resin. Specific examples include polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyolefins such as polyethylene and polypropylene, and polyamides such as polyphenylene sulfide, nylon 6, and nylon 66. Further, the third component may be added or copolymerized up to 25% of the repeating unit.

As the third component which can be added, for example, inorganic particles typified by titanium oxide, antistatic agents typified by sodium dodecylbenzenesulfonate and the like can be used. Isophthalic acid or the like can be used as a copolymerizable component.

In the present invention, among these, thermoplastic fibers made of polyester are most preferred from the viewpoint of spinnability, high elongation characteristics and the like. In the present invention, the polyester used for the porous support composed of the polyester fiber has an aromatic dicarboxylic acid, an aliphatic dicarboxylic acid, or an alicyclic dicarboxylic acid and a diol as main components, like the film. Preferable examples include polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polycyclohexane dimethylene terephthalate, and a copolymer of ethylene terephthalate and ethylene isophthalate. Particularly preferred are polyethylene terephthalate and polyethylene naphthalate from the viewpoint of thermal stability during perforation.

The basis weight of the porous support comprising the thermoplastic fiber of the present invention is preferably ² to ²⁰ g / m ² , more preferably 3 to 15 g / m ² , and particularly preferably 5 to 1 g / m ² .
0 g / m ² . When the basis weight is ² to 20 g / m ² , ink permeability is good and image quality and printability are good. Also,
When the basis weight is 5 to 20 g / m ² , more sufficient strength can be obtained.

The average fiber diameter of the thermoplastic fibers constituting the porous support of the present invention is preferably 1 to 20 μm,
More preferably 2 to 15 μm, particularly preferably 2 to 6 μm
m. When the average fiber diameter is 1 to 20 μm, sufficient strength and heat resistance can be obtained, ink permeability is good, and white spots are less likely to occur during printing, which is preferable.

The porous support made of thermoplastic fibers of the present invention is preferably a porous support made of drawn thermoplastic fibers from the viewpoint of mechanical strength and heat resistance.

The crystal melting energy of the porous support (ΔH
u) is preferably 2 in terms of transportability and durability after plate making.
It is 0-65 J / g, more preferably 30-65 J / g. The crystallinity of the porous support is preferably 20% or more, more preferably 30% or more, from the viewpoint of transportability after plate making in perforation.

The degree of orientation of the porous support is determined by birefringence (Δn).
Is preferably 0.05 or more. More preferably, it is 0.10 or more. When the birefringence is 0.05 or more, the transportability after stencil making of the base paper is good. In particular, when the birefringence is 0.15 or more, more sufficient strength can be obtained.

The porous support of the present invention may have the same fiber diameter or a mixture of fibers having different fiber diameters. Further, the porous support is not limited to a single-layer structure, and may have a multilayer structure in which materials having different average fiber diameters are laminated stepwise.

The method for producing a heat-sensitive stencil sheet of the present invention is as follows:
This will be described below.

In the present invention, as the thermoplastic resin, specifically, for example, polyester, polyolefin, or polyamide can be used. Among them, a thermoplastic resin using a polyester is most preferable from the viewpoint of spinnability, high elongation characteristics, and the like, and a method for producing the thermoplastic resin will be described with reference to the case of polyester.

In the present invention, the polyester can be produced by the following method. For example, a method in which an acid component is directly esterified with a diol component, and then the product of this reaction is heated under reduced pressure to remove the excess diol component and polycondensate to produce a dialkyl acid. There is a method of using an ester, performing a transesterification reaction between the ester and a diol component, and then performing polycondensation in the same manner as described above. At this time, if necessary,
As a reaction catalyst, an alkali metal, an alkaline earth metal, manganese, cobalt, zinc, antimony, germanium, or a titanium compound can also be used.

The polyester in the present invention may contain, if necessary, an organic lubricant such as a flame retardant, a heat stabilizer, an antioxidant, an ultraviolet absorber, an antistatic agent, a pigment, a fatty acid ester, or a wax, or a polysiloxane. A foaming agent and the like can be blended. Furthermore, in order to impart lubricity, for example, clay, mica, titanium oxide, calcium carbonate,
Inorganic particles such as kaolin, talc, wet or dry silica, and organic particles containing acrylic acid-based polymers, polystyrene and the like as components can also be blended. Also,
A method of imparting lubricity by so-called internal particles formed by deactivating a catalyst or the like added during the polyester polymerization reaction can also be used.

In the present invention, a porous support comprising a polyester film and polyester fibers can be produced by the following method.

In the present invention, the polyester film is
For example, it can be manufactured by a T-die extrusion method. This is a method of manufacturing a polyester film by extruding the polyester onto a cast drum, and adjusting the slit width of the die, the discharge amount of the polymer, and the number of revolutions of the cast drum, to obtain a polyester film having a desired thickness. Can be manufactured.

In the present invention, the porous support made of polyester fiber can be obtained by using a non-woven fabric produced by a direct melt spinning method such as a melt blow method or a spun bond method using the polyester. Non-woven fabric
It consists of an undrawn fiber with low orientation. The intrinsic viscosity [η] of the polymer used is preferably at least 0.30, more preferably at least 0.40.

In the melt-blowing method, when a molten polymer is discharged from a plurality of orifices arranged in a row in a die, hot air is blown from slits provided on both sides of the orifice row in the nonwoven fabric made of polyester fiber. The polymer discharged is made finer, and then sprayed onto a net conveyor arranged at an appropriate position to collect and form a web. Since the polyester fiber is rapidly cooled from a molten state to a room temperature atmosphere, it is solidified in a state close to amorphous and is finely fined by the pressure of hot air, but is not drawn, and is in a state close to what is called non-orientation. In addition, the fibers are collected in a state where they are fused to each other, and by appropriately adjusting the collection distance between the die and the net conveyor, the degree of fusion of the fibers can be adjusted, and the polymer discharge amount, hot air temperature, hot air By appropriately adjusting the flow rate, the moving speed of the conveyor, and the like, the basis weight and the fiber diameter of the nonwoven fabric can be arbitrarily set. The nonwoven fabric obtained in this way is composed of fibers in which the fiber diameters are not uniform and the thick and thin fibers are moderately dispersed.

In the conventional melt blow method, the molten polymer is finely thinned by high-temperature, high-pressure hot air when discharged from a die. The thinned fiber has a too small fiber diameter and a non-uniform fiber diameter, and in high-magnification stretching, the thin fiber in the fiber group is cut or the porous support breaks because the fiber comes off. Problem. However, in the case of producing a porous support made of polyester fibers in the present invention, the base temperature, the hot air flow rate, the hot air velocity, the hot air temperature, the nonwoven fabric made of ultrafine polyester fibers by adjusting the collection temperature. Good stretchability can be ensured, and stable production can be achieved. As a result, the stretchability with the film is improved, and the film can be stretched to a higher magnification more stably than before, and a highly sensitive heat-sensitive stencil sheet having good flatness can be obtained.

Similarly, in the spunbond method, a porous support made of polyester fiber is pulled by an air ejector on a polymer discharged from a die, and the obtained filaments collide with a collision plate to spread the fibers. It is manufactured using a nonwoven fabric on which a web is formed by collecting the web. By appropriately setting the amount of polymer discharged and the conveyor speed, the basis weight of the porous support can be arbitrarily set. In addition, by appropriately adjusting the pressure and the flow rate of the ejector, the molecular orientation state of the filament can be arbitrarily adjusted.
By reducing the spinning speed by reducing the pressure and flow rate, a porous support made of fibers having a low molecular orientation can be obtained. Further, by adjusting the cooling rate of the discharged polymer, a porous support in which fibers having different crystallinities are mixed can be obtained.

The degree of crystallinity of the unstretched nonwoven fabric made of thermoplastic fiber used in the present invention is preferably 20% or less, more preferably 15% or less, particularly preferably 10% or less in order to sufficiently adhere to the film. is there. On the other hand, the degree of orientation of the unstretched nonwoven fabric made of thermoplastic fibers is preferably low from the viewpoint of stretchability, and the birefringence (Δn) is preferably 0.03 or less. More preferably it is 0.01 or less. More preferably, it is 0.008 or less.

In the heat-sensitive stencil printing paper of the present invention, the bonding between the thermoplastic film and the porous support made of thermoplastic fibers is performed by bonding a vinyl acetate resin, an acrylic resin, a urethane resin, a polyester resin, or the like. Alternatively, the bonding may be performed without using an adhesive. The method for bonding without the use of an adhesive is not particularly limited, but a method of laminating a thermoplastic film and a porous support made of thermoplastic fibers and performing thermocompression bonding is preferred.

The method of thermocompression bonding of the porous support comprising a thermoplastic film and thermoplastic fibers in the present invention is not particularly limited, but thermocompression bonding with a heating roll is particularly preferred in view of easiness of the process. . In the present invention, the thermocompression bonding is preferably performed at a stage before the stretching step after the thermoplastic film is cast. Thermocompression temperature is 50
° C to glass transition temperature (Tg) of thermoplastic fiber + 20 ° C
Is preferred.

Next, the thermoplastic film thermocompressed and the unstretched nonwoven fabric made of thermoplastic fibers are co-stretched. By co-stretching in the state of thermocompression bonding, the film and the porous support can be stretched integrally. In addition, by co-stretching both, the porous support made of thermoplastic fiber serves as a reinforcing member, and the thermoplastic film can be formed extremely stably without being broken.

In the present invention, the above-mentioned "co-stretching" means that the unstretched nonwoven fabric is laminated with a film and then both stretched.

In the co-stretching method of the present invention, biaxial stretching is preferred from the viewpoint of improving the perforation sensitivity of the film and the uniform dispersibility of the fibers forming the porous support made of thermoplastic fibers. The biaxial stretching may be any of a sequential biaxial stretching method and a simultaneous biaxial stretching method. In the case of the sequential biaxial stretching method,
In general, the film is stretched in the longitudinal direction and the transverse direction, but may be stretched in the opposite direction. The stretching temperature is determined by the glass transition temperature (Tg) of the thermoplastic fiber used for stretching and the temperature increase crystallization temperature (Tc).
and c). The stretching ratio is not particularly limited, and is appropriately determined depending on the type of the polymer for the thermoplastic film to be used, the perforation sensitivity required for the heat-sensitive stencil base paper, and the like. . After the biaxial stretching, the film may be stretched longitudinally, horizontally, or vertically and horizontally again. Further, it is also preferable to subject the heat-sensitive stencil printing base paper of the present invention to heat treatment after biaxial stretching. Further, after the heat-sensitive stencil sheet obtained by the treatment is once cooled to about room temperature, it can be further aged at a relatively low temperature of 40 to 90 ° C. for about 5 minutes to 1 week. When such aging is employed, curling and wrinkling are less likely to occur during storage of the heat-sensitive stencil sheet or in a printing machine, which is particularly preferable.

The method for making the transmitted microwave intensity Mx parallel to the longitudinal direction and the transmitted microwave intensity My parallel to the width direction of the heat-sensitive stencil sheet of the present invention satisfy the above-mentioned formula (1) is not particularly limited. Although not to be performed, for example, in the case of forming a porous support by biaxially stretching a nonwoven fabric made of unstretched thermoplastic fibers in the longitudinal direction and the width direction, or an unstretched thermoplastic film and unstretched A base paper satisfying the above formula (1) by adjusting the ratio of the stretching ratio in the longitudinal direction to the stretching ratio in the width direction in the case of biaxially co-stretching after thermally bonding a non-woven fabric made of a thermoplastic fiber. Can be obtained. Further, it is more preferable that the stretching ratio in the longitudinal direction is higher than the stretching ratio in the width direction. Alternatively, a method may be used in which the film is stretched biaxially in the longitudinal direction and the width direction and then stretched again in the longitudinal direction. In addition, there is a method in which an unstretched nonwoven fabric is slightly stretched in the longitudinal direction, and then biaxially co-stretched together with the film. It is also effective to perform stretching in the longitudinal direction in two stages.

In the case where the above method is employed, stable high-magnification stretching can be achieved by using a nonwoven fabric having good stretchability, and a base paper which sufficiently satisfies the formula (1) can be obtained.

The porous support made of thermoplastic fibers has different fiber orientation degree and stretchability by appropriately adjusting and operating spinning conditions (die temperature, hot air flow rate, hot air velocity, hot air temperature, collection temperature) and the like. Things can be done. By using a porous support made of thermoplastic fibers obtained in this manner and having a small heat shrinkage, the above-described stable stretching at a high magnification can be achieved. The thermal shrinkage ratio as used herein means the heat of the thermoplastic fiber constituting the porous support at a glass transition temperature (Tg) of 25 ° C. + 25 ° C. for 10 minutes without tension in both the longitudinal direction and the width direction of the porous support. The shrinkage ratio is preferably 25% or less, more preferably 20% or less.

Regarding the spinning conditions, the flow rate of hot air per cm of the width of the orifice row is preferably 0.005 to 0.15 Nm ³ / min, more preferably 0. 02~0.10Nm is a ³ / min. The hot air velocity is 30
It is preferably from 0.000 to 8000 m / min, more preferably from 3000 to 7000 m / min. About collection temperature, 90-120 ° C from fusion strength between fibers and drawability
And more preferably 100 to 120 ° C.

Further, by subjecting the obtained porous support made of thermoplastic fiber to heat treatment before subjecting it to co-stretching, a porous support having a small heat shrinkage and good stretchability can be obtained. For example, there is a method in which a porous support is placed in an oven and heat-treated. In this case, the heat treatment temperature is 5
0 to 150 ° C. is preferred, and the heat treatment time is 0.5 seconds to 10 seconds.
Minutes are preferred.

The heat-sensitive stencil printing paper of the present invention has a silicone oil, a silicone-based resin, a fluorine-based resin, a surfactant, an antistatic, for preventing fusing at the time of perforation on one side of the film which is to be in contact with the thermal head. Agents, heat stabilizers, antioxidants, organic particles, inorganic particles, pigments, dispersing aids, preservatives,
It is preferable to provide a thin layer made of an antifoaming agent or the like. The thickness of the thin layer for preventing fusion is preferably 0.005 to 0.4 μm.
m, more preferably 0.01 to 0.4 μm.

When a thin layer for preventing fusion is provided on the heat-sensitive stencil sheet of the present invention, the coating solution is applied in the form of a coating solution dissolved, emulsified or suspended in water, and then the water is removed by drying or the like. Is preferred. The coating may be performed before or after stretching the film. In order to make the effect of the present invention more remarkable, when performing sequential biaxial stretching such as transverse stretching after longitudinal stretching, before transverse stretching,
When simultaneous biaxial stretching is performed, it is particularly preferable to apply before stretching. The application method is not particularly limited, but application is preferably performed using a roll coater, a gravure coater, a reverse coater, a bar coater, or the like. In addition, before applying a thin layer for preventing fusion, if necessary,
An activation treatment such as a corona discharge treatment may be performed in various other atmospheres. <Method for measuring characteristics> (1) Transmitted microwave intensity: Five square samples each cut to a length of 10 cm in the longitudinal direction and the width direction of the base paper were collected. The sample was measured with a molecular orientation meter (MOA-2001A type) manufactured by KS Systems, and expressed as an average of five samples. (2) Melting point (Tm), Glass transition temperature (Tg), Temperature rise crystallization temperature (Tcc): Using a differential scanning calorimeter RDC220, manufactured by Seiko Electronics Co., Ltd., sample 5 mg, and heat up from room temperature Raise the temperature at 20 ° C./min. At this time, the DSC curve is bent due to a change in specific heat based on the transition from the glassy state to the rubbery state, and is sensed in such a manner that the baseline moves in parallel. The intersection of the tangent to the base line at the temperature below the inflection point and the tangent to the point where the inclination is maximum at the inflection point was defined as the start point of inflection, and this temperature was defined as the glass transition temperature (Tg). Further, the peak value of the exothermic curve based on crystallization was defined as a heating crystallization temperature (Tcc), and the peak value of the endothermic curve based on crystal melting was defined as a melting point (Tm). (3) Crystal melting energy (ΔHu) of a porous support composed of a thermoplastic film and a thermoplastic fiber: The sample is determined from the area at the time of melting using a differential scanning calorimeter RDC220 type manufactured by Seiko Instruments Inc. The area from the melting start temperature position to the end position is connected by a straight line, and this area (a) is obtained. Measure In (indium) under the same DSC conditions,
This area (b) is obtained. Crystal melting energy (ΔH
u) was calculated from the following equation.

ΔHu = 28.5 × a / b (J / g) (4) Crystallinity: The sample was put into a density gradient tube made of an aqueous solution of sodium bromide, and the value after 10 hours had elapsed was read to determine the density. Was. The crystallinity of the sample was calculated from the following equation, with the amorphous density being 1.335 g / cm ³ and the crystal density being 1.455 g / cm ³ .

Crystallinity (%) = 100 × (density of sample−
1.335) / (1.455-1.335) (5) Intrinsic viscosity [η]: After drying the sample at 105 ° C. for 20 minutes, 0.1 ± 0.005 g was weighed, and o-chlorophenol 10 The mixture was stirred at 100 ° C. for 15 minutes in × 10 ⁻⁶ m ³ and dissolved. After cooling, Yamato Robotic AVM-10
The viscosity at 25 ° C. was measured with an S-type automatic viscosity meter, and the specific viscosity η _sp was determined and calculated by the following Haggins equation.

Η _sp / c = [η] + k ′ [η] ² c (where k ′ = 0.343, c is a solution of 1 × 10 ⁻⁴ m ³
It is the concentration expressed in the number of g dissolved therein. (6) Average fiber diameter: The average fiber diameter was determined by taking 10 photographs of an arbitrary 10 places of the porous support with an electron microscope at a magnification of 2000 times, and arranging 15 arbitrary fibers per photograph. The diameter was measured and this was done for 10 pictures, for a total of 1
The average value was obtained by measuring the diameter of 50 fibers. (7) Weight per unit area: A value obtained by carefully peeling off the thermoplastic film from the heat-sensitive stencil sheet, cutting the porous support into 20 × 20 cm, measuring the weight, and converting the weight to the weight per square meter. (8) Birefringence (Δn): By laser Raman spectroscopy,
Apparatus RamanorT-64000 (JobinYvo
n / Atago Bussan), the birefringence (Δn) was determined by the following equation.

Birefringence (Δn) = 275 × (I _yy -I _xx )
/ (I _yy + 2I _xx ) I _xx : Raman band intensity in a deflection arrangement perpendicular to the longitudinal direction of the porous support single yarn I _yy : Raman band in a deflection arrangement parallel to the porous support single yarn longitudinal direction Strength (9) Mass printability evaluation: Heat-sensitive stencil sheet was supplied to RISOGRAPH “GR377” manufactured by Riso Kagaku Kogyo Co., Ltd. Plate making was performed using 8 charts (manufactured by Riso Kagaku Kogyo Co., Ltd.) as a manuscript, 3000 sheets were printed, and the presence or absence of wrinkles on the plate making master wound around the drum during printing was determined as follows.

Wrinkles were not generated at all after printing 3,000 sheets. “」 ”: Wrinkles were generated at 2,000 to 3,000 prints,“ O ”: Wrinkles were generated at 1,000 to 2,000 prints. The sample that was wrinkled before the number of printed sheets was 1,000 was evaluated as “x”. "△" and above are practical levels. (1
0) Evaluation of image quality: Heat-sensitive stencil printing paper was supplied to RISOGRAPH "GR377" manufactured by Riso Kagaku Kogyo Co., Ltd., and a "NEWS" chart (Riso Kagaku Kogyo Co., Ltd.) was used as a manuscript. Printing was done. With respect to the 100th image, the white spot defect in the solid black portion was visually observed and determined as follows.

No white defect was generated at all, “◎”: less than 5 white defects, “○”: 5 to 10 white defects, “△”: white defect Are more than 10 were marked as "x". "△" and above are practical levels.

[0056]

The present invention will be described below with reference to examples, but the present invention is not limited to these examples. Example 1 A rectangular spinneret having a hole diameter of 0.30 mm, a number of holes of 130, and a row of orifices was used.
g / min, hot air flow rate 0.055 Nm ³ / min, hot air temperature 29
At 5 ° C, a polyethylene terephthalate raw material (intrinsic viscosity =
0.494) by a melt blow method, and the fibers were collected on a conveyor at a collection temperature of 100 ° C. to give a basis weight of 100 g /
The unstretched nonwoven fabric made of polyester fibers m ² was produced. The average fiber diameter of the polyester fibers constituting the obtained nonwoven fabric was 8.0 μm.

The nonwoven fabric sheet was stretched 5.0 times in the longitudinal direction, then stretched 2.5 times in the width direction, and heat-treated at a temperature of 160 ° C. to have a fiber diameter of 4.3 μm and a basis weight of 8.0 g / m ^2. ,
Birefringence of support single yarns arranged parallel to the longitudinal direction 0.19
1 porous support was produced. The porous support and a 1.5 μm-thick biaxially stretched polyester film were adhered with a vinyl acetate adhesive, and a water-soluble release agent was applied to the film surface to prepare a heat-sensitive stencil sheet. Table 1 shows the evaluation results. Example 2 A fiber was prepared in the same manner as in Example 1 except that the stretching ratio was 4.5 times in the longitudinal direction and 3.0 times in the width direction with a nonwoven sheet having a basis weight of 110 g / m ^2. Diameter 4.
A heat-sensitive stencil sheet having a birefringence of 0.181 of a support single yarn arranged at ² μm, a basis weight of 8.1 g / m ² and parallel to the longitudinal direction was prepared. Table 1 shows the evaluation results. Example 3 A fiber was prepared in the same manner as in Example 1 except that a nonwoven fabric sheet having a basis weight of 85 g / m ² was stretched 3.5 times in the longitudinal direction and 3.0 times in the width direction. Diameter 4.4
[mu] m, basis weight 8.1 g / m ^2, to prepare a heat-sensitive stencil sheet of birefringent 0.162 support single yarn arranged parallel to the longitudinal direction. Table 1 shows the evaluation results. Example 4 A rectangular spinneret having a hole diameter of 0.30 mm, a number of holes of 130, and a row of orifices was used.
g / min, hot air flow rate 0.055 Nm ³ / min, hot air temperature 29
At 5 ° C, a polyethylene terephthalate raw material (intrinsic viscosity =
0.494) by a melt blow method, and the fibers were collected on a conveyor at a collection temperature of 100 ° C. to give a basis weight of 110 g /
The unstretched nonwoven fabric made of polyester fibers m ² was produced. The average fiber diameter of the polyester fibers constituting the obtained nonwoven fabric was 8.0 μm.

Next, a raw material of a copolymer of ethylene terephthalate and ethylene isophthalate having an ethylene isophthalate copolymerization amount of 14 mol% was supplied to a hopper, and then a T-die die was formed using an extruder having a screw diameter of 40 mm. The polyester film was extruded at a temperature of 270 ° C. and cast on a cooling drum (60 ° C.) having a diameter of 600 mm to produce a polyester film.

On the polyester film, an unstretched non-woven fabric made of the polyester fiber was placed, supplied to a heating roll, and thermocompressed at a roll temperature of 75 ° C. The polyester film surface of the laminated sheet thus obtained was preheated at 85 ° C., and the nonwoven fabric surface made of polyester fiber was
After stretching at 5 ° C. and then heating at 95 ° C. with a stretching roll made of silicone rubber (pressure roll pressure 1.5 N / cm),
The film is stretched 2.5 times in the longitudinal direction, and then stretched 1.8 times in the longitudinal direction using a silicone rubber stretching roll heated to 97 ° C. (pressure roll pressure: 1.5 N / cm). The film was stretched in the longitudinal direction. Subsequently, it was sent to a tenter type stretching machine and stretched 3.0 times in the width direction at 95 ° C.
Further, heat treatment was performed at 140 ° C. for 5 seconds in a tenter to prepare a heat-sensitive stencil sheet. The film thickness of the polyester film of the heat-sensitive stencil sheet was 1.5 μm. A water-soluble release agent was applied to the polyester film surface of the heat-sensitive stencil sheet at the entrance of the tenter using a gravure coater. The polyester fiber constituting the porous support of the obtained heat-sensitive stencil printing base paper has an average fiber diameter of 4.2 μm, a basis weight of 8.1 g / m ² , and supports arranged in parallel to the base paper longitudinal direction. The birefringence of a single yarn is 0.18
It was 4. Table 1 shows the evaluation results. Example 5 In Example 4, only the unstretched nonwoven fabric sheet was supplied to a longitudinal stretching machine, preliminarily stretched 1.2 times in the longitudinal direction, and wound up. Next, the pre-stretched nonwoven fabric and the unstretched film were stacked and supplied to a heating roll, and thermocompression-bonded at a roll temperature of 75 ° C. The polyester film surface of the laminated sheet thus obtained is preheated at 85 ° C., then the nonwoven fabric surface of the polyester fiber is preheated at 95 ° C., and then a silicone rubber stretching roll heated to 95 ° C. (pressing roll pressure 1. 5
N / cm) and stretched 3.75 times in the longitudinal direction. Subsequently, it was sent to a tenter type stretching machine and stretched 3.0 times in the width direction at 95 ° C. 5 minutes at 140 ° C inside the tenter
Heat treatment was performed for 2 seconds to produce a heat-sensitive stencil sheet. The film thickness of the polyester film of the heat-sensitive stencil sheet was 1.5 μm. A water-soluble release agent was applied to the polyester film surface of the heat-sensitive stencil sheet at the entrance of the tenter using a gravure coater. The average fiber diameter of the polyester fibers constituting the porous support of the obtained heat-sensitive stencil sheet is 4.2 μm, and the basis weight is 8.1.
At a g / m ² , the birefringence of the support single yarn arranged in parallel with the longitudinal direction of the base paper was 0.170. Table 1 shows the evaluation results. Comparative Example 1 A fiber was prepared in the same manner as in Example 1 except that the stretch ratio was stretched 3.0 times in the longitudinal direction and 3.5 times in the width direction using a nonwoven fabric sheet having a basis weight of 85 g / m ^2. Diameter 4.4
A heat-sensitive stencil sheet having a thickness of 8.1 g / m ² , a birefringence of a support single yarn arranged in parallel in the longitudinal direction, and a birefringence of 0.143 was produced. Table 1 shows the evaluation results. Comparative Example 2 A fiber was prepared in the same manner as in Example 1 except that the stretching ratio was 2.5 times in the longitudinal direction and 4.0 times in the width direction with a nonwoven fabric sheet having a basis weight of 80 g / m ^2. Diameter 4.5
A heat-sensitive stencil sheet having a thickness of 8.0 g / m ² , a birefringence of a support single yarn arranged in parallel in the longitudinal direction, and a birefringence of 0.131 was produced. Table 1 shows the evaluation results. Comparative Example 3 The procedure of Example 4 was repeated, except that the unstretched nonwoven fabric made of polyester fiber was stretched 3.0 times in the longitudinal direction and 3.5 times in the width direction at a basis weight of 85 g / m ^2. The evaluation was performed to prepare a heat-sensitive stencil sheet having a fiber diameter of 4.4 μm, a basis weight of 8.1 g / m ² , a birefringence of a support single yarn arranged in parallel in the longitudinal direction of 0.145, and a film thickness of 1.5 μm. Table 1 shows the results. Comparative Example 4 In Example 4, only an unstretched nonwoven fabric sheet having a basis weight of 80 g / m ² was supplied to a longitudinal stretching machine, preliminarily stretched 1.2 times in the longitudinal direction, and wound. Next, the pre-stretched nonwoven fabric and the unstretched film were stacked and supplied to a heating roll, and thermocompression-bonded at a roll temperature of 75 ° C. The polyester film surface of the laminated sheet thus obtained is preheated at 85 ° C., then the nonwoven fabric surface of the polyester fiber is preheated at 95 ° C., and then a silicone rubber stretching roll heated to 95 ° C. (pressing roll pressure 1. 5 N / cm), stretched 2.5 times in the longitudinal direction, and subsequently stretched roll made of silicone rubber heated to 97 ° C. (pressing roll pressure 1.5 N / cm)
Then, the film was stretched 2.0 times in the longitudinal direction, and stretched in the longitudinal direction in two stages. Next, it is sent to a tenter type stretching machine,
The film was stretched 2.0 times in the width direction at 95 ° C. Further, heat treatment was performed at 140 ° C. for 5 seconds in a tenter to prepare a heat-sensitive stencil sheet. The film thickness of the polyester film of the heat-sensitive stencil sheet was 1.5 μm. A water-soluble release agent was applied to the polyester film surface of the heat-sensitive stencil sheet at the entrance of the tenter using a gravure coater. Polyester fibers constituting the porous support of the obtained heat-sensitive stencil printing base paper have an average fiber diameter of 4.5 μm, a basis weight of 8.0 g / m ² , and supports arranged in parallel to the longitudinal direction of the base paper. The birefringence of the single yarn was 0.197. Table 1 shows the evaluation results. In the base paper, wrinkles were generated at the time of plate formation, and many printing defects due to the wrinkles were conspicuous.

[0060]

[Table 1]

[0061]

According to the present invention, even when a large number of sheets are printed, print wrinkles are hardly generated on the base paper, and a high quality printed matter can be obtained.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H114 AB23 AB24 BA01 BA05 DA56 DA73 DA76 4F100 AK22G AK41A AK41B AK42 AT00A BA02 CB00 DG01B DG15 DJ00 EJ38 GB90 HB31 JA13 JA20 JB16A JB16B JN18 YY00

Claims (6)

[Claims] 1. A heat-sensitive stencil base paper comprising a thermoplastic film and a porous support comprising thermoplastic fibers,
A stencil sheet for heat-sensitive stencil printing, wherein the transmitted microwave intensity Mx parallel to the longitudinal direction of the base paper and the transmitted microwave intensity My parallel to the width direction satisfy the following expression. 1.0 <My / Mx ≦ 2.0 2. The base paper for heat-sensitive stencil printing according to claim 1, wherein the thermoplastic fiber is a polyester fiber. 3. The heat-sensitive stencil sheet according to claim 1, wherein the birefringence of the porous support is 0.05 or more. 4. The porous support has a basis weight of 2 to 20 g / m 2.
Thermal stencil sheet according to any one of claims 1 to 3, characterized in that it is ^2. 5. The base paper for heat-sensitive stencil printing according to claim 1, wherein the thermoplastic film is a polyester film. 6. The heat-sensitive stencil printing paper according to claim 1, wherein Mx and My satisfy the following expressions. 1.2 ≦ My / Mx ≦ 2.0