JP2002192851A - Master for thermal stencil printing and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a master for thermal stencil printing having excellent perforating sensitivity and plate wear resistance in the master for the stencil printing having a porous resin film made of a resin on one surface of a thermoplastic resin film and a method for manufacturing the same. SOLUTION: 1. The master for the thermal stencil printing comprises at least the porous resin film made by coating a fluid on the thermal resin film and drying the fluid. When air gap holes of the resin film are each regarded as being a circle and converted in terms of a true circle, a mean hole size of the film as observed from the film side is larger tan that observed from the resin film side. 2. The method for manufacturing the master for the thermal stencil printing comprises the steps of coating the fluid set to a soluble state by mixing a synthetic resin with a plurality of solvents having different solubilities in a prescribed thickness on the thermoplastic resin film, and drying to form the porous resin film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a halogen lamp,
The present invention relates to a master for heat-sensitive stencil printing which is made by flash irradiation with a xenon lamp or a flash valve, infrared irradiation, pulse irradiation with a laser beam or the like, or perforation and perforation by a thermal head or the like, and a method for producing the master.

[0002]

2. Description of the Related Art Conventionally, a thermosensitive stencil master in which porous thin paper made of natural fibers or synthetic fibers alone or as a mixture is adhered with an adhesive is used as an ink-permeable support on a thermoplastic film. However, the master for thermal stencil printing using a porous thin paper made of such fibers as a support has the following problems. (1) By laminating the porous thin paper and the film using an adhesive, the adhesive accumulates like a bird's web between the fibers of the porous thin paper, and it is difficult for the thermal head to pierce at that portion, The passage of ink is hindered, and printing unevenness is likely to occur. (2) The fibers of the porous tissue paper themselves impede the passage of ink,
Printing unevenness is likely to occur. (3) The smoothness of the film surface is reduced due to the fiber texture of the porous thin paper, the adhesion to the thermal head is poor, and an unperforated portion is formed, so that printing unevenness occurs.

Some proposals have been made to improve such problems, but none have been satisfactory. For example, JP-A-3-193445 discloses that
It has been proposed to use thin paper made of synthetic fibers having a fineness of 1 denier or less as a porous support, but it is not sufficient to solve the above problem. JP-A-62-1984
No. 59 proposes a method for forming a porous support by printing a radiation-curable resin pattern having a substantially closed shape in a thermoplastic film by gravure, offset, flexo, or the like. However, with this printing method, it is difficult to reduce the line width of the resin pattern to 50 μm or less, and the printed portion cannot be perforated, resulting in printing unevenness.

JP-A-3-240596 discloses an ink jet ink having a low viscosity in which a dispersion comprising a water-dispersible polymer and colloidal silica is applied to the surface of a thermoplastic film, dried and provided with a porous support. A printing method for printing has been proposed. However, according to this method, the pore diameter of the porous layer is small, and the conventionally used printing ink for stencils has poor ink passage, so that a sufficient printing density cannot be obtained.

On the other hand, Japanese Patent Application Laid-Open No. 54-33117 proposes a master for heat-sensitive stencil printing which does not use a porous support and is substantially made of a thermoplastic film. This method has a high heat shrinkage and a film thickness of 3 μm
The following films have good printability due to good perforation by a thermal head, but have a problem that they are too stiff to be conveyed by a printing machine. If a thick film is used to improve transportability, the perforation by the thermal head will decrease,
Printing unevenness occurs.

The present inventors have previously proposed a thermosensitive stencil master in which a porous resin film is provided on one side of a thermoplastic film (JP-A-7-139918, JP-A-7-30).
No. 5105). However, in these, the porous resin film formed by applying and drying the fluid on the thermoplastic film has a lower strength and the printing durability of the master than the thin paper conventionally used for bonding with the film. There was a problem of shortage. In particular, in order to obtain good perforation sensitivity, when the pores of the porous resin film are large and the trunk is narrowed, the porous resin film becomes brittle, the master elongates during printing, and the collapse of the porous resin film. There is a problem that the print density is reduced due to the collapse.

[0007] In order to compensate for the insufficient strength of the porous resin film, the present inventors disclosed in Japanese Patent Application Laid-Open Nos. 10-147075 and 10-236011 a resin on one surface of a thermoplastic resin film. Having a porous resin film consisting of
Furthermore, a heat-sensitive stencil master has been proposed in which a porous fiber membrane made of a fibrous substance is laminated on the surface, and the elongation of the master during printing of the master has been improved. However, the problem that the print density is lowered has not been completely solved.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances of the prior art, and has a porous resin film made of a resin on one surface of a thermoplastic resin film. It is an object of the present invention to provide a master for heat-sensitive stencil printing which is excellent in both perforation sensitivity and printing durability and a method for producing the same.

[0009]

In order to increase the sensitivity of the master, it is preferable that the porous resin film has large voids and a narrow trunk, but this reduces the film strength and increases the elongation of the master during printing. In addition, problems such as a decrease in print image density are likely to occur. Further, the effect of controlling the amount of ink passing through the porous resin film is lost, and the set-off is deteriorated.

In view of the above, the present inventor has proposed a thermosensitive stencil master having at least a porous resin film formed by applying and drying a fluid on a thermoplastic resin film, and the pore size of the porous resin film on the film side is reduced. While large and advantageous for perforation sensitivity, the pore diameter on the opposite side is small, so that the porous film has a shape that is advantageous for printing durability and control of the amount of ink passed. When converted into a perfect circle by considering the circle, the average pore diameter when observed from the film side is 1.2 times to 4.0 times the average pore diameter observed from the porous resin membrane side.
By making the number twice, it was found that a master for heat-sensitive stencil printing which solved the above problems was obtained, and the present invention was able to be achieved.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The master for heat-sensitive stencil printing of the present invention is obtained by applying a fluid on a thermoplastic resin film and drying to form a porous resin film. A porous fiber membrane may be laminated on the porous resin membrane to improve printing durability and transportability, or a functional layer may be provided between the film and the porous resin membrane to improve curl and rigidity. A thin film may be provided.

In the present invention, as the thermoplastic resin film, polyester, polyamide, polypropylene,
Conventionally known materials such as polyethylene, polyvinyl chloride, polyvinylidene chloride or a copolymer thereof are used, and a polyester film is particularly preferably used from the viewpoint of perforation sensitivity. As the polyester used for the polyester film, preferably, polyethylene terephthalate,
Copolymers of ethylene terephthalate and ethylene isophthalate, copolymers of hexamethylene terephthalate and cyclohexane dimethylene terephthalate, and the like can be given. Particularly preferred for improving perforation sensitivity are copolymers of ethylene terephthalate and ethylene isophthalate, and copolymers of hexamethylene terephthalate and cyclohexane dimethylene terephthalate.

The thermoplastic resin film of 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 dye, a fatty acid ester, or a wax. An antifoaming agent such as siloxane can be blended. Further, lubricity can be imparted as required. There is no particular limitation on the method of imparting lubricity, but, for example, clay, mica, titanium oxide, calcium carbonate, kaolin, talc, inorganic particles such as wet or dry silica, acrylic acid, organic particles containing styrene and the like as constituents And the like, a method using internal particles, a method of applying a surfactant, and the like.

In the present invention, the thickness of the thermoplastic resin film is usually preferably 0.1 μm to 5.0 μm,
More preferably, it is 0.1 μm to 3.0 μm. If the thickness exceeds 5.0 μm, the piercing property may decrease,
If the thickness is less than 0.1 μm, the film formation stability may be deteriorated, and the printing durability may be reduced.

The definition of the functional thin film in the present invention is as follows. 1. A thin film that improves the adhesion between a thermoplastic film and a porous resin film. 2. Thin film that improves curl. 3. A thin film that improves the rigidity of the master. 4. A thin film that does not hinder the perforation sensitivity when the master is perforated by the thermal head and further improves the perforation properties. 5. A thin film that improves the strength of the film. In addition, if it satisfies any one of the above functions 1 to 5, it corresponds to the functional thin film of the present invention.

As the resin material constituting the functional thin film,
For example, vinyl resins such as polyvinyl acetate, polyvinyl butyral, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, styrene-acrylonitrile copolymer and the like, polyamides such as polybutylene and nylon, polyphenylene oxide, (Meth) acrylic esters, polycarbonates, polyester resins, polyether resins, polyurethane resins, copolymers, mixtures, and modified products thereof are used. Furthermore, various fillers, antistatic agents, stick preventive agents, surfactants, preservatives, defoamers, plasticizers, modifiers, and the like can be used in a range that does not impair the effects of the present invention.

The functional thin film is formed by applying a functional thin film coating solution prepared in advance on a thermoplastic film and drying. The coating liquid is often a solution of the above materials in a solvent. As a method of applying the functional thin film coating solution to the thermoplastic resin film, a commonly used coating method such as a blade, a transfer roll, a wire bar, a reverse roll, a gravure, and a die can be used.
There is no particular limitation.

It is preferable to use a polyisocyanate in combination to improve the adhesiveness. In particular, it is preferable to use a polyester polyol, a polyether polyol, a polyurethane resin and a polyisocyanate in combination.
In order to improve the piercing property of the thermal head, it is preferable to use a polyester polyol, a polyether polyol, a polyurethane resin having a softening point of 40 ° C to 150 ° C, and an isocyanate in combination. Here, the molar ratio of OH group / NCO group is from 1 / 0.1 to 1/20, but may be appropriately selected according to the required characteristics. To lower the softening point of the functional thin film, a resin having a low softening point may be used, or a plasticizer or the like may be added.

The thickness of the functional thin film after drying is 0.01 μm
To 2.0 μm, more preferably 0.1 μm to 1.0 μm.
μm is more preferred. If it is smaller than 0.01 μm, the effect of improving adhesion, stiffness and curl is small, and
If it exceeds m, the heat perforation sensitivity is adversely affected. The material of the functional thin film and the thickness after drying are actually determined by several experiments. When biaxially stretched polyester is used as the film and butyral resin is used as the porous resin film,
As the functional thin film, polyester, a reaction product of a polyol and an isocyanate, an isocyanate polymer, and the like can be suitably used.

The porous resin film in the present invention may have a structure having a large number of voids inside and on the surface of the film, and the voids have a thickness within the porous resin film from the viewpoint of ink permeability. Those having a continuous structure in the direction are desirable.

In the present invention, the average pore size of the porous resin membrane observed from the side without the film is generally 2 μm to 50 μm.
m, preferably 5 μm to 30 μm. Average pore size 2
If it is less than μm, the ink permeability is poor. Therefore, if a low-viscosity ink is used in order to obtain a sufficient amount of ink passing, a phenomenon occurs in which the printing ink oozes from the side of the printing drum or the rear end of the wound master during printing. On the other hand, if the average pore diameter exceeds 50 μm, the effect of suppressing the ink by the porous resin film is reduced, and the ink between the printing drum and the film is excessively extruded during printing, causing problems such as back stains and bleeding. I do.
That is, if the average pore size is too small or too large, good print quality cannot be obtained. In particular, when the average pore diameter of the voids in the porous resin film is 30 μm or less, the thicker the porous resin film layer is, the more difficult it is for the printing ink to pass through. Therefore, the transfer amount of the ink to the printing paper is controlled by the thickness of the layer. can do. If the thickness of the layer is not uniform, printing unevenness may occur. Therefore, it is desirable that the thickness be uniform.

The pore size of the porous resin membrane observed from the film side is 1.2 times or more the pore size observed from the side without the film.
It is preferably 4.0 times. When the ratio is less than 1.2 times, the porosity in the porous resin film is often low, and it is easy to hinder perforation by the thermal head. Also,
When the ratio exceeds 4.0 times, the strength of the porous resin film in the portion in contact with the film becomes weak, and the porous resin film is crushed at the time of printing, which tends to induce a decrease in print density during printing. When forming the porous resin film, a thin film without voids may be formed at the interface between the porous resin film and the film, but in the present invention, regardless of the presence or absence of the thin film, the porous resin film The pore size shall be measured.

Even when a functional thin film exists between the porous resin film and the film, the pore size of the porous resin film is measured in the same manner. Observation with an optical microscope, especially when observed from the film side, may enter the field of view to a part that does not directly affect the perforation sensitivity of the master due to the depth of field of the microscope, but in the present invention The pore size of the porous resin film is measured by the pore size visible on the surface.

The thickness of the porous resin film of the present invention is from 2 μm to
It is 100 μm, preferably 5 μm to 50 μm. 2μ
If it is less than m, the porous resin film hardly remains behind the perforated portion after perforation by the thermal head, and the back transfer of the printed matter is likely to occur without controlling the amount of transferred ink. Also,
The effect of the porous resin film to suppress the amount of ink transferred is greater as the film is thicker, and the amount of ink transferred to the paper during printing can be adjusted by the thickness of the porous resin film.

The density of the porous resin film is usually 0.01 g /
In cm ³ ~1g / cm ^3, preferably 0.1g / cm ³ ~
0.7 g / cm ³ . When the density is less than 0.01 g / cm ³ , the strength of the film is insufficient, and the film itself is easily broken. 1g
If it exceeds / cm ³ , the ink permeability during printing will be poor.

The adhesion amount of the porous resin film is 0.1 g / m ²
３５35 g / m ² , preferably 0.5 g / m ² 225 g / m
^2, in particular 1g / m ² ~11g / m ² is preferred. An increase in the amount of adhesion impedes the passage of ink and deteriorates the image quality.
If it is less than m ² , it will be difficult to control the amount of ink transfer.
If it exceeds 5 g / m ² , the passage of the ink is hindered and the image deteriorates.

Examples of the resin material constituting the porous resin film include polyvinyl acetate, polyvinyl butyral, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, styrene-acrylonitrile copolymer and the like. Examples thereof include vinyl resins, polyamides such as polybutylene and nylon, polyphenylene oxide, (meth) acrylate, polycarbonate, polyurethane, cellulose derivatives such as acetylcellulose, acetylbutylcellulose and acetylpropylcellulose. Each of the above resins may be used as a mixture of two or more.

In order to control the formation, strength, pore size and the like of the porous resin film, it is desirable to add an additive such as a filler to the porous resin film as needed. Here, the filler is a concept including pigments, powders, and fibrous substances. Among them, needle-like fillers are particularly preferable.
Specific examples include magnesium silicate, sepiolite, potassium titanate, wollastonite, zonotolite, mineral needle fillers such as gypsum fiber, non-oxide needle whiskers, oxide whiskers, and double oxide whiskers. Etc., and plate-like fillers such as mica, glass flake, and talc. As the pigment, not only inorganic but also organic pigments, organic polymer particles such as polyvinyl acetate, polyvinyl chloride, and polymethyl acrylate, and zinc oxide, titanium dioxide, calcium carbonate, and silica can be used.

The amount of these additives is preferably 5% to 200% based on the resin. If it is less than 5%, the flexural rigidity due to the addition of the additive does not increase. Conversely 2
If it exceeds 00%, the adhesion to the film will be poor.

In the porous resin film of the present invention, an antistatic agent, a stick preventing agent,
Surfactants, preservatives, defoamers and the like can be used in combination.

Next, a method for forming the porous resin film of the master for heat-sensitive stencil printing of the present invention will be described. The first method for forming a porous resin film is to form a porous film in a drying process by applying a coating liquid obtained by dissolving and / or dispersing a resin in a mixed solvent of a good solvent and a poor solvent. It is. At this time, a good solvent needs to be a combination that evaporates easily at a lower temperature than a poor solvent. When one good solvent and one poor solvent are used, respectively, the boiling point of the good solvent must be relatively lower than the boiling point of the poor solvent. The selection of a good solvent and a poor solvent is optional, but generally, when the difference in boiling point is 15 ° C. to 40 ° C., a porous resin film having desired characteristics is easily formed. If the boiling point difference is less than 10 ° C., the evaporation time difference between the two solvents is small, and the formed film is unlikely to have a porous structure. If the boiling point of the poor solvent is too high, drying takes a long time and the productivity is poor, so the boiling point of the poor solvent is desirably 150 ° C. or lower.

The resin concentration in the coating solution varies depending on the material used, but is 5% to 30%. If it is less than 5%, the opening diameter becomes too large, and the thickness of the porous resin film tends to be uneven. Conversely, if it exceeds 30%, it is difficult to form a porous resin film, or even if it is formed, the pore size becomes small and it is difficult to obtain desired characteristics. The average pore size of the porous resin film is affected by the poor solvent in the atmosphere. In general, the higher the ratio to the good solvent, the larger the amount of coagulation and the larger the average pore size.

Since the addition ratio of the poor solvent varies depending on the resin and the solvent, it must be appropriately determined by experiments. Typically,
The pore size of the porous resin film increases as the amount of the poor solvent increases. If the amount of the poor solvent is too large, the resin precipitates and the coating liquid becomes unstable.

The ratio of the pore size observed from the film side of the porous resin film to the pore size observed from the non-film side can be controlled as follows. If it takes time to dry the coating liquid for forming the porous resin film, the growth of the voids on the side close to the film proceeds, and the difference in the pore diameter increases. Also, when the viscosity of the coating solution is low, the gap on the film side tends to be large. The drying time of the coating solution can be controlled by the ambient temperature during drying, the amount of air blow, and the like. The viscosity of the coating solution is determined by the formulation such as the solid content concentration and the molecular weight of the resin.

The second method for forming a porous resin film is, for example, as disclosed in Japanese Patent Application Laid-Open No. H11-235885, by applying a fluid mainly composed of a W / O emulsion onto a thin film, This is a method in which the water is mainly formed into holes through which the ink passes after drying, and the resin in the solvent (which may contain additives such as fillers and emulsifiers) becomes a structure. is there. In this second method for forming a porous resin film, in order to adjust the formation, strength, pore size, and stiffness of the porous film, if necessary in the porous film, in addition to the hollow filler, Additives such as fillers can be added. Among them, needle-like, plate-like, or fibrous fillers are particularly preferable.

HLB (Hydrophiric-Lyophir1c Balanc) is relatively lipophilic for the formation of W / O emulsions.
e) Surfactants with 4 to 6 are effective, but H
When a surfactant having an LB of 8 to 20 is used, a more stable and uniform W / O emulsion can be obtained. The use of a polymeric surfactant is also one of the methods for obtaining a more stable and uniform emulsion. Addition of a thickener such as polyvinyl alcohol or polyacrylic acid to an aqueous system is effective for stabilizing the emulsion.

The ratio of the pore size observed from the film side of the porous resin film to the pore size observed from the non-film side can be controlled as follows. When the viscosity of the coating liquid for forming a porous resin film is low, or when the stability of the emulsion is low, the pore size observed from the film side tends to be larger than the pore size observed from the non-film side.
In a W / O emulsion, when the film is dried with the film facing down, an aqueous phase having a large particle size tends to settle and collect at a position close to the film, and an aqueous phase having a small particle size tends to collect upward.
When the viscosity of the coating liquid is low, the movement of the aqueous phase is facilitated, and the pore size observed from the film side tends to be larger than the pore size observed from the side without the film. When the stability of the emulsion is low, the aqueous phase tends to coalesce in the emulsion, and the aqueous phase having a large particle size due to coalescence tends to settle. As a result, the pore diameter observed from the film side tends to be larger than the pore diameter observed from the side without the film.

The viscosity of the coating solution is determined by the formulation such as the solid content concentration, the molecular weight of the resin, and the ratio of the aqueous phase to the oil phase. Also,
The stability of the coating solution can be controlled not only by the emulsification method but also by the formulation, especially the type and amount of the surfactant.

The method for forming the porous resin film of the present invention is not limited to the method exemplified above.

As a method for applying the coating solution for forming a porous resin film of the present invention to a thermoplastic resin film, coating methods generally used conventionally such as a blade, a transfer roll, a wire bar, a reverse roll, a gravure, and a die are used. A method can be used, and there is no particular limitation.

The strength of the porous resin film tends to be lower than that of the porous thin paper used for the conventional master for heat-sensitive stencil printing. For this reason, when printing is performed, the porous resin film is crushed in the thickness direction, the ink permeability is deteriorated, and the image density may be reduced. In order to stabilize the print image density in printing using the master of the present invention, it is effective to reduce the voids of the porous resin film or to reduce the porosity, but then the ink permeability of the master deteriorates. As a result, the print image density becomes low.
Therefore, instead of these methods, if the amount of the porous resin film attached is reduced, the thickness of the porous resin film is reduced, and the change in print density due to crushing during printing is reduced. However, if this state is maintained, problems may occur in the transferability and printing durability of the master. Therefore, it is preferable to stack a porous fiber film on the porous resin film. A master on which a porous fiber membrane is laminated can be a means for achieving both high ink permeability and print density stability.

As the porous fiber membrane in the present invention,
Mineral fiber such as glass, sepiolite, various metals, animal fiber such as wool and silk, natural fiber such as cotton, manila hemp, mulberry, mitsumata, pulp, regenerated fiber such as soup and rayon, and synthesis of polyester, polyvinyl alcohol and acrylic Thin paper such as fibers, semi-synthetic fibers such as carbon fibers, and inorganic fibers having a whisker structure are exemplified.

In this case, it is necessary to select an appropriate thickness of the fibrous substance depending on the perforated diameter of the thermoplastic resin film, the thickness of the film, and the like, but the diameter is 20 μm or less, preferably 1 μm to 10 μm. If the diameter is smaller than 1 μm, the tensile strength is weak, and if the diameter is larger than 20 μm, ink passage is hindered and so-called white spots due to fibers appear on the image. The length of the fibrous material is 0.1 mm to 1 mm.
It is preferably about 0 mm, more preferably 1 mm to 6 mm
It is about. If it is shorter than 0.1 mm, the tensile strength becomes weak, and if it is longer than 10 mm, uniform dispersion becomes difficult.

The basis weight of the porous fiber membrane in the present invention is preferably 1 g / m ^{2 to} 20 g / m ^2, more preferably 3 g / m ² .
/ M ^{2 to} 10 g / m ² . If the basis weight is more than 20 g / m ² , the penetrability of the ink is reduced and the image clarity is reduced. When the basis weight is less than 1 g / m ² , sufficient strength as a support may not be obtained.

The method for producing a porous fiber membrane comprising a fibrous substance according to the present invention is not particularly limited, but it may be a paper made by short-fiber wet-making, a nonwoven fabric or a woven fabric, or a screen. It may be gauze or the like, and papermaking paper is preferably used in terms of productivity, cost and the like.

The adhesive strength between the thermoplastic resin film and the porous resin film of the master for thermosensitive stencil printing of the present invention, and the adhesive strength between the porous resin film and the porous fiber film when the porous fiber film is provided. Is preferably at least 1.4 N / m, more preferably at least 2.8 N / m. If the adhesive strength is less than 1.4 N / m, peeling occurs during handling and transport, causing not only wrinkles but also elongation during printing, peeling, and tearing. The upper limit of the adhesive strength is not particularly limited as long as ink passage is not hindered.

In the present invention, the adhesive used for laminating the porous fiber membrane is preferably in a state of high viscosity so as not to block the pores of the porous resin membrane from the ink-permeable surface, and is preferably used. The viscosity until the adhesive is completely cured is 1
00 cps or more, and more preferably 300 cps or more.

According to the present invention, a method for manufacturing a master for heat-sensitive stencil printing when a porous fiber film is bonded includes a coating solution for forming a porous resin film on one surface of a thermoplastic resin film. It is preferable that after the outermost layer of the porous resin film is dried and formed into a film, it is bonded to the porous fiber layer to which the adhesive has been applied. If the porous fiber membrane is laminated before the porous resin membrane is formed,
The formation of the porous resin film is hindered, and a desired porous resin film cannot be obtained. Also, since the adhesive may block the pores of the porous resin film, it is preferable to apply the adhesive to the porous fiber film.

In order to form a porous resin film having excellent ink permeability, which is the object of the present invention, a thermoplastic resin is preferably used. In this case, when a solvent-type adhesive is used as the adhesive, the porous resin film is eroded and the pores are closed, so that it is preferable that there is no solvent at least at the time when the porous resin film and the porous fiber film are laminated. From this side, a solventless adhesive or an aqueous / emulsion adhesive is used.

In order to obtain the predetermined adhesive strength of the present invention and to satisfy the above conditions, a polyurethane-based adhesive is used. As the polyurethane-based adhesive of the present invention, a solventless polyurethane adhesive capable of obtaining a desired adhesive strength with a small amount of adhesion is used. In addition, since a porous fiber membrane containing inexpensive natural fibers is preferably used, an aqueous / emulsion type polyurethane adhesive causes expansion and contraction of the porous fiber membrane at the time of coating, which deteriorates curl and the like. Also, a solventless polyurethane adhesive is used.

Examples of the solventless polyurethane adhesive include a one-pack moisture-curable urethane prepolymer obtained by reacting a polyol component such as polyether polyol or polyester polyol having hydroxyl groups at both terminals with an isocyanate component, or a polyol component. Examples include a two-part curable adhesive divided into isocyanate components, but are not particularly limited. Hexamethylene diisocyanate (HMDI), 2,4-
Diisocyanate-1-methylcyclohexane, 2,6
-Diisocyanate-1-methylcyclohexane, diisocyanate cyclobutane, tetramethylene diisocyanate, o-, m- and p-xylylene diisocyanate (XDI), dicyclohexylmethane diisocyanate, dimethyldicyclohexylmethane diisocyanate, hexahydrometoxylidene diisocyanate (H
XDI), and resinous or alicyclic diisocyanates such as lysine diisocyanate alkyl ester (the alkyl portion of the alkyl ester preferably has 1 to 6 carbon atoms): toluylene-2,4-cyisocyanate ( TD1), toluylene-2,6-diisocyanate, diphenylmethane-4,4'-diisocyanate (MDI), 3-methyldiphenylmethane-4,
4'-diisocyanate, m- and p-phenylene diisocyanate, chlorophenylene-2,4-diisocyanate, naphthalene-1,5-diisocyanate, diphenyl-4,4'-diisocyanate, 3,3'-dimethyldiphenyl-4,4 '-Diisocyanate, 1,
Aromatic diisocyanates such as 3,5-triisopropylbenzene-2,4-diisocyanate and diphenylether diisocyanate, and mixtures thereof.

The adhesive can be applied by any method such as a blade coating method, a reverse roll coating method, a gravure coating method, a knife coating method, a spray coating method, an offset gravure coating method, a kiss coating method, and a bar coating method. There is no particular limitation.

The surface on which the adhesive is applied may be applied to either the porous resin film or the porous fiber film. However, in order not to close the opening of the porous resin film, the surface is coated on the porous fiber film. It is better to do.

When a solvent-free polyurethane adhesive is applied to the porous fiber membrane, if the viscosity is too high, the fibers fall off and coating failure occurs. Therefore, the viscosity is lowered by heating the roll, and the coating is performed at 3000 cps or less. Is preferred. More preferably, it is preferable to apply between 300 cps and 1500 cps. If the viscosity is less than 300 cps, there is a possibility that the openings will be closed after lamination with the porous resin film and the ink permeability will be impaired. If the viscosity exceeds 3000 cps, the fibers of the porous fiber layer will easily fall off.

When a non-solvent adhesive is used, it is preferable to cure the heat-sensitive stencil master wound in a roll shape in order to accelerate the reaction. The curing temperature is preferably 50 ° C. or lower, more preferably 40 ° C.
It is as follows. If it exceeds 50 ° C., the thermoplastic resin film shrinks, and the problem of curling occurs. The curing time is not particularly limited as long as it is performed until the desired adhesive strength is obtained.

As an application method of the adhesive of the present invention, there is a method in which an application liquid diluted with an organic solvent such as ethyl acetate is applied to the porous fiber layer, dried, and then bonded to the porous resin film. However, a method in which the coating is performed without a solvent is preferred from the viewpoints of environmental aspects and residual solvents.

The amount of the adhesive to be applied is different from that of the conventional stencil master (laminated product of the thermoplastic resin film and the porous fiber membrane) having the same structure as the conventional one, and it is necessary to consider the influence of the perforation inhibition. There is no particular limitation as long as the desired adhesive strength is obtained, but it is sufficient that the pores of the porous resin membrane and the porous fiber membrane are not closed, and preferably 0.05 g / m ^2. to 5.0 g / m ^2, more preferably in the range of ^{0.1g / m 2 ~3.0g / m 2} .

The master for heat-sensitive stencil printing of the present invention uses a silicone oil, a silicone resin, a fluororesin, a surfactant, an antistatic agent to prevent fusing at the time of perforation on one side of the film to be in contact with the thermal head. Agent, heat-resistant agent,
It is desirable to provide a thin film comprising an antioxidant, organic particles, inorganic particles, pigments, dispersing aids, preservatives, defoamers, and the like.
The thickness of the thin film for preventing fusion is preferably 0.005 μm or more.
0.4 μm, more preferably 0.01 μm to 0.4 μm
It is.

The method of providing the above-mentioned thin film for preventing fusion is not particularly limited, but it is preferable to apply a solution diluted with water, a solvent, or the like using a roll coater, a gravure coater, a reverse coater, a bar coater, or the like, and then dry. preferable.

Hereinafter, a method for measuring the characteristics of the master for heat-sensitive stencil printing of the present invention will be specifically described. (Method of measuring characteristics) 1) Average pore diameter of porous resin film The porous resin film of the master was placed on the film side and the side without the film by an optical microscope (Olympus BX60 magnification 2).
00 times. Lighting is reflected light, level 9. The polarizing filter is used at the position where the sharpness is most effective. ) Observe and capture images into a computer. (The focus is adjusted to the surface of the porous resin film. (The sample is gradually brought closer to the eyepiece of the optical microscope, and the focus is first focused on the porous resin film.)) The image processing software “WinROOF” ( The image is binarized using Mitani Shoji Co., Ltd.), and the average pore size (converted into a perfect circle) is determined. The binarization procedure is as follows: gray image conversion, density conversion (default), automatic binarization (P
Tile method, default), fill in holes, delete (less than 100), measure (shape feature-area). In the case of a master in which a porous fiber film is laminated on a porous resin film, photographing from the side without the film is completed before laminating the porous fiber film in the stage of preparing the master.

2) Adhesive Strength Adhesive Strength Between Thermoplastic Resin Film and Porous Resin Film When the thermosensitive stencil master of the present invention has a porous fiber film, only the porous fiber film is peeled from the master. . This operation is unnecessary if the master does not have a porous fiber membrane. Next, a cellophane tape is adhered to the surface of the porous resin film opposite to the film so that air does not enter, and the measurement is performed by a 90-degree peel test in accordance with JIS K6854-1. At this time, the measurement is performed by fixing the porous resin film to which the cellophane tape is stuck and pulling the thermoplastic resin film. When the porous fiber membrane alone cannot be peeled off, the measurement is performed by fixing the laminate of the porous fiber membrane and the porous resin membrane without attaching the cellophane tape. Even when a functional thin film is present between the thermoplastic resin film and the porous resin film, the adhesive strength between the thermoplastic resin film and the porous resin film can be increased by the above method without regard to the presence of the functional thin film. It shall be measurable. Adhesive strength between porous resin film and porous fiber film (only when the heat-sensitive stencil master of the present invention has a porous fiber film) Peel off only the thermoplastic resin film from the heat-sensitive stencil master of the present invention, A cellophane tape is stuck on the surface of the porous resin film from which the thermoplastic resin film has been peeled off so that air does not enter, and measurement is performed by a 90-degree peeling test in accordance with JIS K 6854-1. At this time, the porous resin film to which the cellophane tape was stuck is fixed, and the porous fiber film is subjected to tensile measurement. When only the thermoplastic resin film cannot be peeled off, the measurement is performed by fixing the laminate of the thermoplastic resin film and the porous fiber membrane without attaching the cellophane tape.

3) Evaluation of printability The prepared master was manufactured by Ricoh Co., Ltd. “Preport JP4”.
000 "(thermal head resolution 40 dpi), and 50mm x 50m
plate making using a manuscript with black solid
Printed. Perforation sensitivity: ◎ for those with the master film part perfectly perforated by the thermal head and a large perforation diameter, も の for those that are perforated completely normally, ○ for those that are perforated but partially reduced in perforation diameter, Those that are not partially perforated are indicated by x. Image quality: The printed matter was evaluated by visual judgment, and a black solid part with conspicuous white spots was evaluated as x, and an intermediate level between ○ and x and a level practically manageable was evaluated as Δ. Set-off: A set having no set-off was evaluated as 、, a set-off at a level that could not withstand double-sided printing was evaluated as x, and a medium intermediate level that could be used in practical use was evaluated as Δ.

4) Evaluation of printing durability Elongation, peeling: The prepared master was supplied to "Priport JP4000" manufactured by Ricoh Co., Ltd., and 6-point characters and 50 mm × 50 m were obtained by a thermal head plate making method.
Plate making and printing were performed using a document having a black solid color of m. The printing speed was 3,000 sheets as standard. If an abnormal image such as image elongation occurred, X: No defect was found in the image, but if peeling of the film or peeling of the porous fiber membrane was seen on the master after printing, Δ, the master was completely abnormal When no was observed, it was evaluated as ○. Image density change: The value obtained by dividing the image density of the 3000th sheet by the image density of the 50th sheet in the printed matter of the printing durability test was 0.9.
When it was less than 5, it was evaluated as ×, when 0.95 or more and less than 0.98, Δ, when 0.98 or more and less than 0.99, 未 満, and when 0.99 or more and 1.01 or less, ◎.

5) Evaluation of transportability In the above evaluations of 3) and 4), those which could be transported without any problems were evaluated as ○, wrinkles and the like occurred during transport as ×, and wrinkles occurred during transport. Those that had no effect on the above were rated as △.

[0065]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto. In addition,
All parts shown below are based on weight.

(Examples 1 to 5, 9 and Comparative Example 1) Polyvinyl acetal resin (manufactured by Sekisui Chemical Co., Ltd., Eslek KS-1) 3.2 parts talc (manufactured by Nippon Talc, Microace LG) 4 parts Sorbitan fatty acid ester (manufactured by Nikko Chemicals Co., Ltd., SO-15) 0.1 part Modified silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd., KF6012) 0.1 part Acrylic polymer O / W emulsion (manufactured by Johnson Polymer, Joncryl) -711) 0.2 parts or more are dissolved and dispersed in ethyl acetate, and water (HEC1
% Solution) was added slowly with stirring to obtain a cloudy porous resin film forming coating solution. Ethyl acetate and water (HEC1
% Solution) depends on the solid content concentration of each coating solution shown in Table 1. The ratio of both is 1.5 ethyl acetate to water (HEC).
(1% solution) is 1.0. Apply each of the above coating solutions at 20 ° C 50
% RH, coated on a 2.0 μm-thick biaxially stretched polyester film with a gravure roll so that the adhesion amount after drying becomes the value shown in Table 1, 50 ° C., 50% RH
After drying in an atmosphere to form a porous resin film, the film was wound into a roll. Anti-fusing agent coating liquid formulation: Silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd., SF8422) 0.5 part Surfactant (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., Plysurf A208) 0.5 part Toluene 100.0 parts An anti-fusing agent coating solution is applied and dried using a bar coater on the surface of the thermoplastic resin film opposite to the porous resin film so that the adhesion amount after drying is about 0.05 g / m ^2. A heat-sensitive stencil master was obtained. The prepared heat-sensitive stencil master was evaluated by the evaluation method described above. Table 2 shows the results.

(Example 6) Functional thin film coating solution Polyester resin 30% ethyl acetate solution (Toyobo Co., Byron 50AS) 25.0 parts Ethyl acetate 185.0 parts Polyester resin 30% ethyl acetate solution (Toyobo Co., Ltd.) (Byron 50AS), was diluted with ethyl acetate to obtain a functional thin film coating solution. The above-mentioned functional thin film coating liquid is applied on a biaxially stretched polyester film having a thickness of 2.0 μm,
By drying at 0 ° C., a functional thin film having a thickness of 0.05 μm was obtained. Further, the coating liquid for forming the porous resin film used in Example 2 was applied on a gravure roll in an atmosphere of 20 ° C. and 50% RH so as to have an adhesion amount of 6.0 g / m ² after drying with a gravure roll. The film was dried in a 50 ° C. RH atmosphere to form a porous resin film and wound up in a roll. Next, the anti-fusing agent of Example 1 was applied using a bar coater on the surface of the thermoplastic resin film opposite to the porous resin film so that the amount of adhesion after drying was about 0.05 g / m ^2. Dry to obtain a thermosensitive stencil master. The prepared heat-sensitive stencil master was evaluated by the evaluation method described above. Table 2 shows the results.

(Example 7) The coating liquid 2 for forming a porous resin film used in Example 2 was gravure rolled on a 2.0 μm-thick biaxially stretched polyester film in an atmosphere of 20 ° C. and 50% RH. After drying, application was performed so that the adhesion amount was 3.0 g / m ^2, and drying was performed at 50 ° C. and 50% RH atmosphere to form a porous resin film, which was wound into a roll. Subsequently, as a porous fiber membrane, a paper made of 100% natural fiber (basis weight 10 g)
/ M ² , thickness 33 μm) and a one-component urethane adhesive (Takenate A260, manufactured by Takeda Pharmaceutical Co., Ltd.) using a roll coater heated to 100 ° C., at an application amount of 0.2 g / m ^2.
After rolling, coating was performed, and lamination was performed with the porous resin film surface of the roll prepared earlier. The viscosity of the adhesive at the time of application was about 1000 cps. Next, the adhesion amount after drying of the anti-fusing agent coating solution used in Example 1 was about 0.05 g.
/ M ² , applied to the surface of the thermoplastic resin film opposite to the porous resin film using a bar coater, dried and wound up, cured at 30 ° C. for 3 days, and used for heat-sensitive stencil printing. Got the master. The prepared heat-sensitive stencil master was evaluated by the evaluation method described above. Table 2 shows the results.

Example 8 The coating solution for forming a porous resin film used in Example 2 was dried on a biaxially stretched polyester film having a thickness of 2.0 μm by a gravure roll in an atmosphere of 20 ° C. and 50% RH. Thereafter, application was performed so that the adhesion amount was 3.0 g / m ^2, and drying was performed at 50 ° C. and 50% RH atmosphere to form a porous resin film, which was wound into a roll. Subsequently, as a porous fiber membrane, a paper made of two types of polyester fibers having a fineness of 0.2 denier and 1.1 denier (basis weight 8 g / m ² ,
(Thickness: 25 μm), a two-component reactive urethane adhesive (manufactured by Takeda Pharmaceutical Co., Ltd., polyol component: Takelac A230, isocyanate component: A30, mixing ratio: 1)
0: 8) was rolled using a roll coater heated to 70 ° C. so that the coating amount was 0.7 g / m ^2, and then applied, followed by lamination with the porous resin film surface of the previously prepared roll. . The viscosity of the adhesive at the time of application was about 800 cps.
Then, a bar coater was applied to the surface of the thermoplastic resin film opposite to the porous resin film so that the amount of the anti-fusing agent coating solution used in Example 1 was about 0.05 g / m ² after drying. And dried and wound up.
After curing for one day, a master for heat-sensitive stencil printing was obtained. The prepared heat-sensitive stencil master was evaluated by the evaluation method described above. Table 2 shows the results.

Example 10 The coating liquid 2 for forming a porous resin film used in Example 2 was dried with a gravure roll on a biaxially stretched polyester film having a thickness of 2.0 μm in an atmosphere of 20 ° C. and 50% RH. Thereafter, application was performed so that the adhesion amount was 3.0 g / m ^2, and drying was performed at 50 ° C. and 50% RH atmosphere to form a porous resin film, which was wound into a roll. Saturated polyester adhesive (UE3500, manufactured by Unitika Ltd.) 15.0 parts Toluene 75.0 parts A coating solution obtained by dissolving and mixing the above was dried using a direct gravure coater to have an application amount of 0.2 g / m ² . Paper made of 100% natural fibers (basis weight 10 g /
m ² and a thickness of 33 μm), and superposed on the porous resin film surface of the previously prepared roll, followed by drying at 50 ° C. Then, a bar coater was applied to the surface of the thermoplastic resin film opposite to the porous resin film so that the amount of the anti-fusing agent coating solution used in Example 1 was about 0.05 g / m ² after drying. To obtain a heat-sensitive stencil master of the present invention. The prepared heat-sensitive stencil master was evaluated by the evaluation method described above. Table 2 shows the results.

Example 11 Polyvinyl Butyral (manufactured by Denki Kagaku Kogyo Co., Ltd., PVB3000-2) 8.0 parts Ethyl alcohol 73.0 parts Water 19.0 parts After dissolving polyvinyl butyral in ethyl alcohol, water was stirred. Was dropped and mixed to obtain a coating liquid for forming a porous resin film. This solution was dried with a gravure roll in an atmosphere of 20 ° C. and 50% RH, and the adhesion amount was 6.0 g / m ^2.
And dried in an atmosphere of 20 ° C. and 50% RH to form a porous resin film and wound up in a roll. Next, the coating amount of the anti-fusing agent coating liquid of Example 1 after drying was about 0.5.
The surface of the thermoplastic resin film opposite to the porous resin film was coated with a bar coater so as to have a thickness of 05 g / m ^2.
After drying, a master for heat-sensitive stencil printing was obtained. The prepared heat-sensitive stencil master was evaluated by the evaluation method described above. Table 2 shows the results.

(Example 12) Polyvinyl butyral (manufactured by Denki Kagaku Kogyo Co., Ltd., PVB3000-2) 8.0 parts Ethyl alcohol 69.0 parts Water 23.0 parts After dissolving polyvinyl butyral in ethyl alcohol, water was stirred. Was dropped and mixed to obtain a coating liquid for forming a porous resin film. This solution was dried with a gravure roll in an atmosphere of 20 ° C. and 50% RH, and the adhesion amount was 6.0 g / m ^2.
And dried in an atmosphere of 20 ° C. and 50% RH to form a porous resin film and wound up in a roll. continue,
A one-component urethane adhesive (manufactured by Takeda Pharmaceutical Co., Ltd., using a roll coater heated to 100 ° C.) on a paper made of 100% natural fiber (basis weight 10 g / m ² , thickness 33 μm) as a porous fiber membrane. Taken A260) was rolled and applied such that the coating amount was 0.05 g / m ^2, and the roll was laminated with the porous resin film surface of the previously prepared roll. The viscosity of the adhesive at the time of application was about 1000 cps. Then, a bar coater was applied to the surface of the thermoplastic resin film opposite to the porous resin film so that the amount of the anti-fusing agent coating solution used in Example 1 was about 0.05 g / m ² after drying. And dried and wound up, and cured at 30 ° C. for 3 days to obtain a heat-sensitive stencil master. The prepared heat-sensitive stencil master was evaluated by the evaluation method described above. Table 2 shows the results.

(Comparative Example 2) Polyvinyl butyral (manufactured by Denki Kagaku Kogyo Co., Ltd., PVB3000-2) 12.0 parts Ethyl alcohol 71.0 parts Water 17.0 parts After dissolving polyvinyl butyral in ethyl alcohol, water was stirred. Was dropped and mixed to obtain a coating liquid for forming a porous resin film. This solution was dried with a gravure roll in an atmosphere of 20 ° C. and 50% RH, and the adhesion amount was 6.0 g / m ^2.
And dried in an atmosphere of 50 ° C. and 50% RH to form a porous resin film and wound up in a roll. Next, the coating amount of the anti-fusing agent coating liquid of Example 1 after drying was about 0.5.
The surface of the thermoplastic resin film opposite to the porous resin film was coated with a bar coater so as to have a thickness of 05 g / m ^2.
After drying, a master for heat-sensitive stencil printing was obtained. The prepared heat-sensitive stencil master was evaluated by the evaluation method described above. Table 2 shows the results.

Example 13 Polyvinyl butyral (PVB3000-2, manufactured by Denki Kagaku Kogyo Co., Ltd.) 8.0 parts Ethyl alcohol 67.0 parts Water 25.0 parts After dissolving polyvinyl butyral in ethyl alcohol, water was stirred. Was dropped and mixed to obtain a coating liquid for forming a porous resin film. This solution was dried with a gravure roll in an atmosphere of 20 ° C. and 50% RH, and the adhesion amount was 6.0 g / m ^2.
And dried in an atmosphere of 20 ° C. and 50% RH to form a porous resin film and wound up in a roll. Next, the coating amount of the anti-fusing agent coating liquid of Example 1 after drying was about 0.5.
The surface of the thermoplastic resin film opposite to the porous resin film was coated with a bar coater so as to have a thickness of 05 g / m ^2.
After drying, a heat-sensitive stencil master of the present invention was obtained. The prepared heat-sensitive stencil master was evaluated by the evaluation method described above. Table 2 shows the results.

[0075]

[Table 1]

[0076]

[Table 2]

Evaluation results from the preceding table: (1) In Example 1, the perforation sensitivity was slightly lower, but the print density stability was higher. (2) In Example 2, there is no problem in any of the standard sample, printability, printing durability, and transportability of the present invention. (3) In Example 3, the printing density stability is low, but the perforation sensitivity is high. (4) In Comparative Example 1, the printing density stability is high, but the perforation sensitivity is poor. (5) In Example 4, although the perforation sensitivity was slightly low, the print density stability was excellent. (6) In Example 5, although the print density stability is slightly low, the perforation sensitivity is excellent. (7) In Example 6, the effect of the functional thin film was
High bonding strength. (8) In Example 7, printing density stability is high because the amount of the porous resin film attached is reduced and the porous fiber film is laminated. (9) In Example 8, the printing density stability is high because the amount of the porous resin film attached is reduced and the porous fiber film is laminated. (10) In Example 9, the amount of the porous resin film attached was reduced, but the printing durability was reduced because the porous fiber film was not laminated. (11) In Example 10, since the adhesive strength of the saturated polyester is low, there is a problem in printing durability and transportability that there is no practical problem. (12) In Example 11, there is no problem in printability, printing durability, and transportability. (13) In Example 12, although there was no problem in print quality, slight peeling was observed between the film and the porous resin film and between the porous resin film and the porous fiber film after the printing durability test. . (14) In Comparative Example 2, the printing density stability is high, but the perforation sensitivity is low, and the image has many white spots. (15) In Example 13, slight peeling was observed because the adhesive strength between the film and the porous resin film was low.

[0078]

According to the first aspect of the present invention, a master having good perforation sensitivity can be obtained. According to the invention of claim 2, a master having both good perforation sensitivity and excellent printing durability can be obtained. According to the third aspect, a master having good adhesion between the porous resin film and the thermoplastic resin film can be obtained. The functional thin film can be expected to have the effect of improving the curl, rigidity, strength, and the like of the master depending on its components. According to the fourth aspect of the present invention, since the printing durability is ensured by the porous fiber film to be laminated, the choice of the resin constituting the porous resin film is wider than when the porous fiber film is not laminated. In addition, since the amount of resin adhered to the porous resin film can be reduced, it is easy to form a porous resin film having high ink permeability. According to the fifth aspect of the present invention, it is possible to obtain a master having no peeling during plate making or printing. According to the sixth aspect of the present invention, a master free from peeling during plate making or printing can be obtained. According to the seventh aspect of the present invention, a master capable of providing a sufficient adhesive strength between the porous resin film and the porous fiber film without deteriorating good print image quality can be obtained.

The invention according to claim 8 is directed to a plurality of solvents (good solvent and poor solvent) having different solubilities of the resin forming the porous resin film.
Are used when they are soluble in each other. Since organic solvents often dissolve in each other well, the choice of solvents is wide, and consequently the range of choice of resins is also wide. A gourd-shaped porous resin film can be easily formed by arbitrarily changing the mixing ratio of the solvent. Further, productivity can be increased by selecting a solvent that evaporates quickly, such as ether or acetone.

The invention of claim 9 uses a good solvent and a poor solvent which do not mix with each other. Compared with the invention of claim 8, since it does not depend on the solubility of the resin, it is less affected by temperature and humidity, and the reproducibility of the formed film shape is high. Since the degree of freedom of formulation is high and the range in which a porous resin film can be formed is wide, it is easy to adjust the viscosity of the coating solution by adjusting the ratio of the oil-water phase, the resin concentration, the resin molecular weight, and the like. Further, in the present invention, if the solid content concentration is the same, the coating liquid has a higher viscosity than the method of the eighth aspect.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of an example of a master for heat-sensitive stencil printing of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Thermoplastic resin film 2 Porous resin film resin part 3 Porous resin film void part 4 Porous fiber film

Claims (9)

[Claims] 1. A master for thermosensitive stencil printing having at least a porous resin film formed by applying and drying a fluid on a thermoplastic resin film, wherein the pores of the porous resin film are regarded as a circle and converted into a perfect circle. Wherein the average pore size when observed from the film side is larger than the average pore size observed from the porous resin film side. 2. When the pores of the porous resin film are regarded as a circle and converted into a perfect circle, the average pore diameter observed from the film side is 1.2 times or more the average pore diameter observed from the porous resin film side. The master for heat-sensitive stencil printing according to claim 1, wherein the ratio is 4.0 times. 3. The master for heat-sensitive stencil printing according to claim 1, wherein a functional thin film is provided between the thermoplastic resin film and the porous resin film. 4. The thermoplastic resin film according to claim 1, wherein a porous fiber film made of a fibrous substance is laminated on the surface of the porous resin film provided on one surface of the thermoplastic resin film. The master for heat-sensitive stencil printing according to any one of the above. 5. The master for heat-sensitive stencil printing according to claim 1, wherein the adhesive strength between the thermoplastic resin film and the porous resin film is 1.4 N / m or more. 6. The master for heat-sensitive stencil printing according to claim 4, wherein the adhesive strength between the porous resin film and the porous fiber film is 1.4 N / m or more. 7. The heat-sensitive stencil according to claim 4, wherein the porous resin film and the porous fiber film are bonded using an adhesive mainly composed of a polyurethane-based adhesive. Master for printing. 8. The method for producing a master for heat-sensitive stencil printing according to claim 1, wherein a fluid obtained by mixing a synthetic resin with a plurality of solvents having different solubilities to form a solubilized state is provided. A method for producing a master for heat-sensitive stencil printing, wherein a porous resin film is formed by applying a fixed thickness on a thermoplastic resin film and drying it. 9. The method for producing a master for heat-sensitive stencil printing according to claim 1, wherein a water-in-oil emulsion containing a dissolved synthetic resin is coated on a thermoplastic resin film with a constant thickness. A method for producing a master for heat-sensitive stencil printing, wherein a porous resin film is formed by coating and drying.