JPH0752573A - Polyester film for high-sensitivity thermal stencil printing base paper - Google Patents

Abstract

PURPOSE:To obtain high-sensitivity thermal stencil printing base paper superior in perforating sensitivity, printing resolution, and resistance to curling. CONSTITUTION:In a biaxially oriented polyester film having a melting point of 150-240 deg.C and a thickness of 0.5-3mum, formulas (1)-(5) are simultaneously met: (1) 16<=S<=40, (2) 80<=F<=270, (3) 3000<=SXF<=7500, (4) 0.02<=Ra<=0.3, and (5) 0.100<=DELTAP<=0.150. In the formulas, S is a heat shrinkage factor (%) after the film is treated at 100 deg.C for 10min, F is a heat shrinkage stress (g/mm<2>) after the film is treated at 100 deg.C for 10sec, Ra is a center line average height (mum), and DELTAP is a face orientation degree.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a polyester film for heat-sensitive stencil printing base paper. More specifically, the present invention relates to a film for high-sensitivity heat-sensitive stencil printing paper, which has excellent perforation sensitivity and curl resistance due to its specific melting point and shrinkage characteristics, and has excellent image resolution and density during printing.

[0002]

2. Description of the Related Art Conventionally, as a base paper for heat-sensitive stencil printing, a laminate of porous thin paper on a thermoplastic resin film such as polyester has been known, and a film used for such application. Is required to have the following characteristics. (1) It is also excellent in handleability and productivity during film production and base paper production. Specifically, during film production, the stretchability is good, troubles such as breakage do not occur, and the winding property and slitting property are also good, and there are no wrinkles or winding deviations at the time of winding. is necessary. Even when the base paper is prepared, it is necessary that the problems such as the unwinding of the film and the running of the film in the process do not occur. (2) It should have strength and elastic modulus sufficient to withstand the work of laminating with porous thin paper and printing. Curling should not occur due to such lamination conditions or changes in temperature and humidity during storage. If the curl becomes large, handling and handling of the stencil in the stencil printing machine become poor, causing problems such as clogging of the stencil.

(3) The thermal perforation sensitivity is good. That is,
It must have sufficient heat-shrinkability so that it can be melted with a small amount of heat and that perforations of an appropriate size can be obtained so that the image during printing becomes clear. (4) The thermal perforation sensitivity does not decrease even when the plate is made many times. That is, it is necessary that the surface-active agent of the release layer, the silicone oil, the molten dust of the film, and the like do not adhere as dirt on the thermal head. (5) Gradation of thermal perforation is good. When used as a base paper, if the portion other than the portion to be perforated is melted due to the influence of the perforations in the periphery, the gradation of the printed image becomes inferior, which is not preferable. That is, it should have a thermal perforation property that allows a clear distinction between the perforated portion and the non-perforated portion.

Conventionally, a biaxially stretched film intended for a thermoplastic resin as a film used for such an application,
A film whose printing characteristics are improved by defining its thermal characteristics (Japanese Patent Laid-Open No. 62-149496) and a film whose surface roughness and the number of protrusions are defined (Japanese Patent Laid-Open No. 63-
No. 227634), or a film having a specified heat shrinkage property (Japanese Patent Laid-Open No. 62-282983, Japanese Patent Laid-Open No. 6-282983).
No. 3-160895, Japanese Patent Application Laid-Open No. 63-321192, Japanese Patent Application Laid-Open No. 3-30996) and the like have been proposed, but all of the above problems cannot be solved.

[0005]

Means for Solving the Problems The inventors of the present invention have made extensive studies in view of the above problems, and as a result, have found that a polyester film having specific characteristics is suitable for use as a base paper for heat-sensitive stencil printing and complete the present invention. Came to.

That is, the gist of the present invention is that the melting point is 150.
A high-sensitivity, heat-sensitive stencil printing base paper film, characterized in that it is a biaxially stretched polyester film having a thickness of 0.5 to 3 μm at ˜240 ° C. and simultaneously satisfies the following formulas (1) to (5). 16 ≦ S ≦ 40 (1) 80 ≦ F ≦ 270 (2) 3000 ≦ S × F ≦ 7500 (3) 0.02 ≦ Ra ≦ 0.3 (4) 0.100 ≦ ΔP ≦ 0.150 (5) [In the above formula, S is the heat shrinkage ratio (%) after the treatment at 100 ° C. for 10 minutes, and F is the heat shrinkage stress after the heat treatment at 100 ° C. for 10 seconds ( g / mm ² ), Ra is the center line average roughness (μm), ΔP
Represents the degree of plane orientation]

The present invention will be described in detail below. The difunctional acid component of the polyester referred to in the present invention is mainly an aromatic dicarboxylic acid or an ester-forming derivative thereof, and specifically, as terephthalic acid, 2,6-naphthalenedicarboxylic acid and an ester-forming derivative thereof. Examples thereof include dimethyl terephthalate and dimethyl 2,6-naphthalenedicarboxylate, and among these, terephthalic acid and dimethyl terephthalate are preferable. Examples of the glycol component include ethylene glycol, butylene glycol, propylene glycol, polyethylene glycol and 1,4-cyclohexanedimethanol, and among them, ethylene glycol and butylene glycol are preferable.

The polyester may be a polyester having one kind of aromatic dicarboxylic acid or its ester-forming derivative and one kind of alkylene glycol as a starting material, but it is a copolymer containing two or more kinds of components. Is preferred. In addition to the above as a component to be copolymerized, for example,
Examples thereof include diol components such as diethylene glycol, neopentyl glycol and polyalkylene glycol, dicarboxylic acid components such as adipic acid, sebacic acid, phthalic acid and isophthalic acid, trimellitic acid and pyromellitic acid. Further, homopolymers each composed of a single component, copolymers containing homopolymers and two or more components, and blended polyesters of the copolymers are preferable. Among them, polybutylene terephthalate and polyethylene terephthalate or isophthalic acid are preferable. A blended polyester with a polyethylene terephthalate copolymer as a copolymerization component is more preferable.

The melting point of the polyester film of the present invention is 1
It is in the range of 50 to 240 ° C, preferably 160 to 230 ° C. When the melting point is higher than 240 ° C, the high perforation sensitivity that is the object of the present invention cannot be obtained, and when the melting point is lower than 150 ° C, the heat-resistant dimensional stability of the film is deteriorated, and the process for producing the base paper and the preservation of the base paper are suppressed. It is not preferable because curl occurs in the inside or gradation of the printed image deteriorates. In the present invention, the difference between the highest melting point (Tm ₂ ) and the lowest melting point (Tm ₁ ) is less than 50 ° C., preferably 3
Although it is lower than 0 ° C., Tm ₁ and Tm ₂ may be the same. If the temperature difference is 50 ° C. or more, uniform perforation does not occur in a short time, and the gradation of the printed image may be deteriorated.

The thickness of the film of the present invention is 0.5 to 3 μm.
m, preferably 0.5-2 μm. More preferably, it is 0.5 to 1.5 μm. When the film thickness is thin, the heat conduction distance is shortened and the heat energy required for perforation is also reduced, so that the perforation property is improved and the resolution and printing quality during printing are improved, but if the thickness is less than 0.5 μm It is not preferable because it is unclear and uneven density is likely to occur, and the printing durability is significantly reduced. On the other hand, when the thickness exceeds 3 μm, the perforation property is deteriorated and unevenness occurs during printing, which is not preferable.

The film of the present invention needs to have a heat shrinkage (S) of 16 to 40%, preferably 18 to 30% after being treated at 100 ° C. for 10 minutes. When S is less than 16%, the perforation sensitivity is insufficient and the print-like image density is lowered, which is not preferable. Further, if S exceeds 40%, unevenness of perforation tends to occur, which is not preferable. Also,
The heat shrinkage stress (F) of the film after treated at 100 ° C. for 10 seconds is 80 to 270 g / mm ² , preferably 100 to
It is 250 g / mm ² . If F is less than 80 g / mm ² , the force for expanding the holes at the time of perforation is insufficient, and perforations having a size large enough to obtain a clear image at the time of printing cannot be obtained, which is not preferable. When F exceeds 270 g / mm ² , uneven thickness, uneven shade or dimensional change occurs, which is not preferable.

In order to obtain a film for a high-sensitivity heat-sensitive base paper which gives good perforation with a low heat source, which is the greatest feature of the present invention, and further has good curl resistance, shrinkage characteristics (heat shrinkage rate) are required in addition to the above-mentioned film characteristics. And heat shrinkage stress) is important. The product of heat shrinkage and heat shrinkage stress (S × F), which is a measure of the balance of shrinkage characteristics, is 3000 to 7500.
Is. If the S × F value is less than 3000, the force for expanding the holes at the time of perforation is insufficient, and perforations having a size large enough to obtain a clear image at the time of printing cannot be obtained, which is not preferable. Further, if the S × F value exceeds 7500, curling occurs due to the lamination conditions or changes in temperature and humidity during storage, resulting in poor handling of the base paper in the stencil printing machine and poor handling of the base paper, and problems such as clogging of the base paper and punching. The thickness is uneven, the density is uneven, or the size is changed, which is not preferable. The normal temperature curl diameter and the 50 ° C. curl diameter are usually 18 mm or more, preferably 20 mm or more. If the room temperature curl diameter and the 50 ° C. curl diameter are less than 18 mm, the transportability of the raw paper in the stencil printing machine may be poor, and troubles such as paper jam may occur. Furthermore, the normal temperature curl diameter and 50
The ratio of the C curl diameter is usually 1.0 to 2.0, preferably 1.
It is 0 to 1.7. If this value exceeds 2.0, curling tends to occur easily due to the lamination conditions or changes in temperature and humidity during storage.

The film of the present invention is used for improving the workability during the winding process during film production, the coating process during base paper preparation, the laminating process and printing, or the fusion between the thermal head and the film during thermal perforation. In order to prevent this, it is preferable to roughen the surface so as to impart appropriate slipperiness to the film, and for that purpose, fine inert particles are usually added to the film. The fine inert particles used in the present invention usually have an average particle size of 0.05.
To 3.0 μm, the particle size distribution value (r) is 1.5 or less, preferably the average particle size is 0.1 to 2.0 μm, and the particle size distribution value (r)
Is 1.4 or less. If the average particle size is less than 0.05 μm, the winding property may be poor. When the average particle size exceeds 3.0 μm or the particle size distribution value (r) exceeds 1.5, the flatness of the film surface is impaired and uneven heat transfer occurs, resulting in non-uniform perforation. However, the resolution may be poor or the print quality may be impaired.

Further, the addition amount of the above particles is usually 0.0
It is 5 to 3% by weight, preferably 0.1 to 2% by weight.
If it is less than 0.05% by weight, the winding property tends to be poor. On the other hand, if it exceeds 3% by weight, the degree of roughening of the film surface is too large, resulting in uneven heat transfer, uneven perforation, poor resolution, and impaired print quality. Examples of the inert particles used in the present invention include silicon oxide, titanium oxide, zeolite, silicon nitride, boron nitride, celite, alumina, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, barium sulfate, calcium phosphate, lithium phosphate. , Magnesium phosphate, lithium fluoride, aluminum oxide, silicon oxide, titanium oxide, kaolin, talc, carbon black, silicon nitride, boron nitride and JP-B-59-521.
The cross-linked polymer fine powder as described in JP-A-6 can be cited as a matter of course, but the present invention is not limited thereto. At this time, the inert particles to be blended may be a single component, or two or more components may be used simultaneously.

The method of blending the inert particles with the polyester in the present invention is not particularly limited, but for example, a method of adding the inert particles to the polyester polymerization step,
Alternatively, a method of melt-kneading before forming into a film is preferably used. In the present invention, a film whose surface is appropriately roughened by the method as described above is obtained, but in order to further satisfy workability, printing resolution, and print quality, the center line average roughness of the film surface is Sa (Ra) is 0.0
2 to 0.3 μm, preferably 0.05 to 0.2 μm
The range is m. Since the film of the present invention is an extremely thin film, the tensile elastic modulus in both the longitudinal direction and the width direction of the film is usually 300 kg / mm ² or more, preferably 350 kg / mm ² or more, so that the handling workability and the durability are improved. Printability becomes better.

Next, the method for producing the polyester film of the present invention will be described. In the present invention, the polymer is supplied to a well-known melt extrusion apparatus typified by an extruder, and heated to a temperature equal to or higher than the melting point of the polymer to melt it.
Next, the melted polymer is extruded from a slit die and rapidly cooled and solidified on a rotating cooling drum to a temperature not higher than the glass transition temperature to obtain a substantially amorphous unoriented sheet. In this case, in order to improve the flatness of the sheet, it is preferable to enhance the adhesion between the sheet and the rotary cooling drum. In the present invention, the electrostatic application adhesion method and / or the liquid coating adhesion method is preferably adopted.

In the present invention, the sheet thus obtained is biaxially stretched to form a film. Describing the stretching conditions specifically, the unstretched sheet is preferably stretched 2 to 4 times at 20 to 100 ° C. in the machine direction. Next, it is stretched in the transverse direction at a temperature of preferably 20 to 100 ° C. by a factor of 2 to 4 to obtain a biaxially oriented film. Preferably, the unstretched sheet is first drawn at 20 to 80 ° C. by a factor of 2 to 3, and further 40 to
The film is longitudinally stretched 1.1 to 1.5 times at 100 ° C. At this time, Δn after longitudinal stretching is preferably 0.080 or less, and more preferably 0.070 or less. Then 50 to 10 laterally
It is stretched 2 to 4 times at 0 ° C. and oriented biaxially. It is also possible to simultaneously biaxially stretch the unstretched sheet so that the area ratio becomes 6 to 40 times.

The film thus obtained may be heat-treated, and if necessary, it may be stretched again in the machine direction and / or the transverse direction before or after the heat treatment. In the present invention, in order to obtain a film having the above-mentioned heat shrinkage property, the stretching ratio is 6 times or more as an area ratio, the heat treatment after stretching is not substantially performed, or 110 ° C. or less even if performed, It is preferable that the temperature is 90 ° C. or lower, the heat treatment time is 1 second to 5 minutes, and the film is stretched within 30% or under a fixed length. The degree of plane orientation (ΔP) of the biaxially stretched film of the present invention is 0.100 to 0.150, preferably 0.1.
It is 10 to 0.135. If ΔP is less than 0.100, uneven thickness, uneven density or dimensional change may occur during perforation, which is not preferable. Further, if ΔP exceeds 0.150, the resolution and printing quality during printing are deteriorated, which is not preferable.

Further, curling, which is considered to be caused by the shrinkage of the film, may occur during the drying step of about 40 to 50 ° C. in the production of the heat-sensitive stencil printing base paper and the long-term storage in the summer. Therefore, in the present invention, in order to prevent curling, when the obtained film is aged at 40 to 70 ° C. for 5 hours to 5 days, preferably at 45 to 60 ° C. for 12 hours to 3 days, the curl resistance becomes good. In the present invention, other polymers (for example, polyethylene, polystyrene, polycarbonate, polysulfone, polyphenylene sulfide, polyamide, polyimide, etc.) can be contained in an amount of about 10% by weight or less based on the total amount of polyester used for film formation. Also, if necessary,
You may mix | blend additives, such as an antioxidant, a heat stabilizer, a lubricant, an antistatic agent, a dye, and a pigment.

[0020]

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to the following examples unless it exceeds the gist thereof. The physical property measuring methods used in the present invention are as follows. (1) Melting point Seiko Electronics Co., Ltd. differential calorimeter SSC580DS
It measured using C20 type. The measurement conditions are as follows. That is, 10 mg of the sample film was set in the DSC apparatus, the temperature was raised at a rate of 10 ° C./min, and 0 to 300
The melting point was measured in the range of ° C, and the melting point was measured as the peak of the melting endothermic peak.

(2) Heat shrinkage ratio (S) 10 times in an oven in which the sample was kept at 100 ° C. without tension.
Heat treatment was performed for a minute, the lengths of the samples before and after the heat treatment were measured, and the heat shrinkage rate was calculated by the following formula.

[Equation 1] Heat shrinkage rate (%) = (sample length before heat treatment-sample length after heat treatment) × 100 / (sample length before heat treatment) Five points were measured in the longitudinal direction and the transverse direction of the film, and the average value was calculated. I asked. (3) Heat shrinkage stress The film was cut into strips with a width of 10 mm, one end was set to the chuck of the load detector and the other was set to the fixed chuck, and the gap between the chucks was set to 50 mm. Immerse the film in an oil bath at 100 ° C without applying an initial load,
The stress value was measured 10 seconds after the start of immersion. The heat shrinkage stress (g / mm ² ) was calculated from the cross-sectional area of the film before immersion.

(4) Curl at room temperature A Japanese film made of Manila hemp fibers was used as a support on a polyester film having a thickness of 1.5 μm, and a vinyl resin was dissolved in toluene as an adhesive. It was dried in an air oven at 50 ° C. for 10 seconds to obtain a heat-sensitive stencil sheet. The obtained base paper was cut into B4 size, the film surface was placed on a flat base, and the curl diameter after 24 hours at 25 ° C. was measured. (5) Curling at 50 ° C. A heat-sensitive stencil sheet was prepared in the same manner as at room temperature curling, the obtained sheet was cut into B4 size, and the film surface was placed on a flat table and 50 ° C.-humidity 90 The curl diameter after treatment for 1 week in a thermo-hygrostat of 1% was measured. (6) Average particle size of fine particles Centrifugal sedimentation type particle size distribution analyzer SA- manufactured by Shimadzu Corporation
The particle size was measured by a sedimentation method based on Stokes's resistance law using CP3 type. The value of 50% integrated (volume basis) in the equivalent spherical distribution of the particles obtained by the measurement was used as the average particle diameter. The particle size distribution value (r) was calculated from the following formula. Particle size distribution value (r) = d ₂₅ / d ₇₅ (In the above formula, d ₂₅ and d ₇₅ are the particle volumes corresponding to 25% and 75% of the total volume measured from the large particle side of the cumulative volume of the particle group. Indicates the diameter (μm)

(7) Center Line Average Roughness (Ra) The surface roughness of the base polyester film is measured according to JIS B0.
According to the method described in 601-1976. For the measurement, a surface roughness meter SE-3F manufactured by Kosaka Laboratory Ltd. was used. Stylus diameter 2 μm, Stylus load 30 mg, Cut-off value 0.08
mm, the measurement length is 2.5 mm, the center line average roughness is obtained, and this is performed at 12 measurement points. Of these, the maximum value and the minimum value are cut, and the average value of 10 points is calculated. R
a. (8) Measurement of Refractive Index of Film Using an Abbe refractometer manufactured by Atago Optical Co., the maximum refractive index nγ in the film plane, the refractive index nβ in the direction perpendicular thereto and the refractive index nα in the thickness direction of the film were measured. The birefringence and the degree of plane orientation were calculated from the following equations. The refractive index was measured at 23 ° C. using sodium D line.

## EQU00002 ## Birefringence (.DELTA.n) = n.gamma.-n.beta. Surface orientation degree (.DELTA.P) = (n.gamma.-n.beta.) / 2-n.alpha. (8) Practical characteristics of heat-sensitive stencil printing base paper . The obtained base paper is applied with a thermal head at an applied energy of 0.0.
A character image and a 16-step gradation image were prepared at 9 mJ and 0.12 mJ. The perforated state of the gradation image area was observed with a microscope from the film side of the plate-making base paper, and the following items were evaluated.

Perforation sensitivity ◎ ... Predetermined perforation is surely performed and the size of perforation is sufficient and very good ○ ... Predetermined perforation is almost certainly performed and the size of perforation is sufficient. There are portions where the prescribed perforations cannot be obtained or where the size of the perforations is insufficient. × ... There are many portions where the prescribed perforations cannot be obtained, and the size of the perforations is insufficient, which is a practical obstacle. Using the plate-making base paper, actual printing was carried out using a lithograph AP7200 printing machine manufactured by Riso Kagaku Kogyo Co., Ltd., and the following characteristics of the obtained characters and images were visually judged. Printing quality ◎ ... Very good with clear density without uneven density and bleeding .... Clear printing without density unevenness and bleeding.
Good △: Slight unevenness in shades and bleeding are recognized and slightly lacking in sharpness × ... Unevenness in shades, or bleeding and blurring are clearly visible

Example 1 Production of Polyester-A Using 100 parts by weight of dimethyl terephthalate and 60 parts of ethylene glycol as starting materials, 0.09 parts by weight of magnesium acetate / tetrahydrate as a catalyst was placed in a reactor and the reaction start temperature was adjusted. The temperature was raised to 150 ° C., the reaction temperature was gradually raised with the evaporation of methanol, and the temperature was raised to 230 ° C. after 3 hours. After 4 hours, the reaction mixture in which the transesterification reaction was substantially completed had an average particle size of 0.70 μm and a particle size distribution value (r) of 1.
10 parts by weight of an ethylene glycol slurry containing 1.0 part by weight of the spherical silica particles of No. 2 was added, and 0.04 part of ethyl acid phosphate, 0.04 part of antimony trioxide was added.
4 parts was added and the polycondensation reaction was carried out for 4 hours. That is,
The temperature was gradually raised from 230 ° C to 280 ° C. On the other hand, the pressure is gradually reduced from normal pressure and finally 0.3 mm
It was Hg. After 4 hours from the start of the reaction, the reaction was stopped and the polymer was discharged under nitrogen pressure. The intrinsic viscosity of the obtained polyester was 0.75.

Production of Polyester-B 100 parts by weight of dimethyl terephthalate, 56 parts by weight of 1,4-butanediol, 0.005 parts of tetrabutyl titanate.
Part by weight is taken in the reactor, the reaction start temperature is set to 150 ° C.,
The reaction temperature was gradually raised as the methanol was distilled off.
After the time, the temperature was set to 210 ° C. After 4 hours, 0.005 parts by weight of tetrabutyl titanate was added to this reaction mixture which had been substantially transesterified, and polycondensation reaction was carried out for 4 hours. That is, the temperature is gradually raised from 210 ° C. to 2
It was set to 60 ° C. On the other hand, the pressure was gradually reduced from atmospheric pressure, and finally set to 0.3 mmHg. After 4 hours from the start of the reaction, the reaction was stopped and the polymer was discharged under nitrogen pressure. The intrinsic viscosity of the obtained polyester was 0.90.

Production of Polyester-C A polyester production-A was prepared in the same manner as in Production-A of polyester except that 80 parts by weight of dimethyl terephthalate and 20 parts by weight of dimethyl isophthalate were used instead of 100 parts by weight of dimethyl terephthalate. Polyester-B was obtained. The intrinsic viscosity of the obtained polyester was 0.76.

50 parts by weight of polyester-A and 50 parts by weight of polyester-B were uniformly blended, extruded into a sheet form from an extruder at 265 ° C., and electrostatically cooled with a rotary cooling drum whose surface temperature was set to 30 ° C. It was rapidly cooled and solidified using the method to obtain a substantially amorphous sheet having a thickness of 13.5 μm. The obtained sheet was lengthwise 2.5 times at 65 ° C.,
Further draw 1.2 times at 75 ℃, then in the transverse direction 80 ℃
The film was stretched to 3.0 times in the above, and then heat treated at 90 ° C. for 6 seconds to produce a biaxially oriented film having a thickness of 1.5 μm. Then, the obtained film was adhered to a porous thin paper according to a conventional method to prepare a base paper for heat-sensitive stencil printing, which was imprinted.

Example 2 A heat-sensitive stencil sheet was prepared in the same manner as in Example 1 except that 50 parts by weight of polyester-C was used instead of 50 parts by weight of polyester-A. I went.

Example 3 A heat-sensitive stencil printing base paper was prepared in the same manner as in Example 1 except that the transverse stretching was 3.3 times, and was imprinted.

Example 4 In Example 1, 50 parts by weight of polyester-A and 50 parts by weight of polyester-B were replaced by polyester-
Heat-sensitive in the same manner as in Example 1 except that 30 parts by weight of A, 30 parts by weight of polyester-B, and 40 parts by weight of the recycled product from the ears and film edges generated during the production of the polyester film of Example 1 were used. A stencil printing base paper was created and imprinted.

Comparative Example 1 In Example 1, 100 parts by weight of polyester-C was used in place of 100 parts by weight of polyester-A, the temperature of the extruder was 280 ° C., and the obtained sheet was machined at 80 ° C. in the machine direction.
A heat-sensitive stencil printing base paper was prepared in the same manner as in Example 1 except that it was stretched 0 times and transversely at 90 ° C. to 3.0 times, and was imprinted.

Comparative Example 2 In Example 1, an unstretched sheet of 24 μm was prepared,
The draw ratio in the longitudinal direction is 4.0 times, and the draw ratio in the transverse direction is 4.
A stencil sheet for heat-sensitive stencil printing was prepared in the same manner as in Example 1 except that the magnification was set to 0, and the imprinting was performed.

Comparative Example 3 A heat sensitive stencil sheet was prepared in the same manner as in Example 1 except that the heat treatment was carried out at 140 ° C. for 6 seconds.
Photographed and printed. The results obtained above are summarized in Tables 1 and 2 below.

[0035]

[Table 1]

[0036]

[Table 2]

[0037]

According to the film of the present invention, the perforation sensitivity,
It is possible to provide a film for high-sensitivity heat-sensitive stencil printing base paper which is excellent in printing resolution and curl resistance, and its industrial value is high.

Claims (1)

[Claims] 1. A melting point of 150 to 240 ° C. and a thickness of 0.5.
A film for high-sensitivity heat-sensitive stencil printing base paper, which is a biaxially stretched polyester film of 3 μm to 3 μm and simultaneously satisfies the following formulas (1) to (5). 16 ≦ S ≦ 40 (1) 80 ≦ F ≦ 270 (2) 3000 ≦ S × F ≦ 7500 (3) 0.02 ≦ Ra ≦ 0.3 (4) 0.100 ≦ ΔP ≦ 0.150 (5) [In the above formula, S is the heat shrinkage ratio (%) after the treatment at 100 ° C. for 10 minutes, and F is the heat shrinkage stress after the heat treatment at 100 ° C. for 10 seconds ( g / mm ² ), Ra is the center line average roughness (μm), ΔP
Represents the degree of plane orientation]