JPH08104071A - Polyester film for high-sensitivity thermal stencil printing base paper - Google Patents

Abstract

PURPOSE: To obtain the high-sensitivity thermal stencil printing base paper film excellent in perforation sensitivity and resistance to curling and resolution and density of an image at the time of printing by a method wherein a biaxially oriented film in use is made of a mixture of two kinds of polyester resins having different melting points and has specific shrink characteristics. CONSTITUTION: A high-sensitivity thermal stencil printing base paper film is made of a 0.5-5μm thick biaxially oriented film obtained from a mixture of 70-95wt.% polyester resin (a) having a melting point of 200-260 deg.C and 5-30wt.% polyester resin (b) having a melting point of 100-200 deg.C and is formed so as to simultaneously meet the following formulas. 30<=ΔTm<=150, 16<=S<=40, 80<=F<=270, 3000<=S×F<=7500, and 0.02<=Ra<=0.3. In the formulas, ΔTm is a melting point difference ( deg.C) between the polyester film (a) and the polyester film (b), S is a thermal shrinkage factor (%) after the film is treated for 10min at 100 deg.C, F is a thermal shrinkage stress (g/mm<2> ) after the film is treated for 10min at 100 deg.C, and Ra is a center line average height (μm).

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 is composed of two or more kinds of polyester resins having a specific melting point and has specific shrinkage characteristics, and thus has excellent perforation sensitivity and curl resistance, and has excellent image resolution and density during printing. The present invention relates to a film for high-sensitivity heat-sensitive stencil printing base paper.

[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 drilling 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 at the time of 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, silicon oil, molten residue 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. In other words, it is necessary to have a thermal perforation property that allows the part to be perforated and the part not to be perforated to be clearly distinguished. Conventionally, a biaxially stretched film intended for a thermoplastic resin as a film used for such an application, the film having improved printing characteristics by defining its thermal characteristics (JP-A-62-149496), surface Of which the roughness and the number of protrusions are specified (Japanese Patent Laid-Open No. 63-227634).
No. JP-A-62-282983, or a film whose heat-shrinking property is defined (JP-A-62-282983, JP-A-63-1608).
Japanese Patent Application Laid-Open No. 95, 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.

[0004]

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, they are composed of two or more kinds of polyester resins having specific melting points and have specific shrinkage characteristics and specific surface roughness. We have found that the biaxially oriented film is suitable as a film for high-sensitivity heat-sensitive stencil printing base paper, and completed the present invention.

That is, the gist of the present invention is that the melting point is 200
70 to 95% by weight of polyester resin (a) at to 260 ° C
And a polyester resin (b) 5 having a melting point of 100 to 200 ° C.
~ 0.5 ~ 5μ thickness obtained from a mixture with ~ 30 wt%
A biaxially stretched film of m having the following formulas (1) to (5)
And a high-sensitivity heat-sensitive stencil printing base paper film.

(2) 30 ≦ ΔTm ≦ 150 (1) 16 ≦ S ≦ 40 (2) 80 ≦ F ≦ 270 (3) 3000 ≦ S × F ≦ 7500 (4) 0.02 ≦ Ra ≦ 0.3 (5) (where ΔTm is the difference (° C.) between the melting points of the polyester resin (a) and the polyester resin (b), and S is 1 at 100 ° C.
Heat shrinkage (%) after treatment for 0 minutes, F is 10 at 100 ° C
Heat shrinkage stress (g / mm ² ) after treatment for seconds, Ra represents center line average roughness (μm))

The present invention will be described in detail below. The polyester resin as referred to in the present invention is a resin whose bifunctional acid component is mainly an aromatic dicarboxylic acid or its ester-forming derivative, and specifically, terephthalic acid, 2,6-naphthalenedicarboxylic acid and its ester-forming derivative. Examples of the derivative include dimethyl terephthalate and dimethyl 2,6-naphthalenedicarboxylate. Among these, terephthalic acid,
Dimethyl terephthalate is preferred. Further, as glycol components, ethylene glycol, butylene glycol, propylene glycol, polyethylene glycol, 1,4
-Cyclohexanedimethanol and the like are mentioned, and among these, ethylene glycol and butylene glycol are preferable. The polyester resin may be a polyester having one kind of aromatic dicarboxylic acid or its ester-forming derivative and one kind of glycol component as a starting material, but is preferably a copolymer containing two or more kinds of components. . In addition to the above as components to be copolymerized, for example, 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. Is mentioned.

An object of the present invention is to provide a base film for heat-sensitive stencil printing base paper which can obtain heat-resistant dimensional stability and high perforation sensitivity even with a small amount of heat. In order to achieve the object of the present invention, the melting point of the polyester resin (a) is 20
It is selected from the range of 0 to 260 ° C, preferably 200 to 250 ° C, more preferably 200 to 240 ° C. When the melting point of the resin (a) exceeds 260 ° C., the film is not melted with a small amount of heat energy, and as a result, perforations having a sufficient size cannot be obtained, which is not preferable. When the melting point of the resin (a) is less than 200 ° C., the heat-resistant dimensional stability when formed into a film is deteriorated, curling occurs during the process of manufacturing the base paper or during storage of the base paper, and the gradation of the printed image is deteriorated. It is inferior, which is not preferable.

The blending amount of the resin (a) is 70 to 95% by weight,
It is preferably in the range of 75 to 90% by weight. Resin (a)
If the blending amount exceeds 95% by weight, sufficient perforation sensitivity cannot be obtained with a small amount of heat energy, which is not preferable. When the content of the resin (a) is less than 70% by weight, the heat-resistant dimensional stability of the film is deteriorated, and curling occurs during the process of manufacturing the base paper or during storage of the base paper, which is not preferable. The melting point of the polyester resin (b) is 100 to 20.
The temperature is 0 ° C, preferably 120 to 180 ° C, more preferably 130 to 170 ° C. The melting point of resin (b) is 2
When the temperature exceeds 00 ° C, the perforation with a small amount of heat energy becomes insufficient, and the high perforation sensitivity aimed at by the present invention cannot be obtained, which is not preferable. The melting point of the resin (b) is 100 ° C
If it is less than the range, the printing becomes unclear and uneven density is likely to occur, and the printing durability is significantly deteriorated, which is not preferable.

The content of the resin (b) is 5 to 30% by weight, preferably 10 to 25% by weight. When the content of the resin (b) exceeds 30% by weight, the heat-resistant dimensional stability of the film is deteriorated, and curling occurs during the process of manufacturing the base paper or during storage of the base paper, which is not preferable.
If the blending amount of the resin (b) is less than 5% by weight, sufficient perforation sensitivity cannot be obtained with a small amount of heat energy, which is not preferable. The greatest feature of the present invention is that the difference in melting point between the polyester resin (a) and the polyester resin (b) (ΔT
m) is 30 to 150 ° C, preferably 40 to 120 ° C, more preferably 50 to 100 ° C. ΔTm is 150
If the temperature exceeds ℃, the heat-resistant dimensional stability when formed into a film deteriorates, and curling occurs during the process of manufacturing the base paper or during storage of the base paper, which is not preferable. When ΔTm is less than 30 ° C., uniform perforation does not occur in a short time and the gradation of the printed image becomes poor, which is not preferable.

The film thickness of the present invention is 0.5 to 5 μm,
Preferably 0.5 to 3 μm, more preferably 0.5 to
2 μm. When the film thickness is thin, the heat conduction distance is shortened, and the heat energy required at the time of punching is also reduced, so that the punching property is improved and the resolution and printing quality at the time of printing are improved, but when the film thickness is less than 0.5 μm However, the printing is unclear and uneven density is likely to occur, and the printing durability is significantly deteriorated, which is not preferable. The film thickness is 5 μm
If it exceeds the range, the perforating property is deteriorated and unevenness occurs during printing, which is not preferable.

The film of the present invention has a heat shrinkage (S) of 16 to 40%, preferably 18 to 30% after being treated at 100 ° C. for 10 minutes. When the S value is less than 16%, the perforation sensitivity is insufficient and the print-like image density is lowered, which is not preferable. Further, if the S value exceeds 40%, uneven drilling tends to occur, which is not preferable. Also, 100 ℃
The heat shrinkage stress (F) of the film after being treated for 10 seconds at 8
0 to 270 g / mm ² , preferably 100 to 250 g /
mm ² . If the F value is less than 80 g / mm ² , the force for expanding the holes during perforation is insufficient, and perforations having a size large enough to obtain a clear image during printing cannot be obtained, which is not preferable. If the F value exceeds 270 g / mm ² , uneven thickness, uneven lightness or dimensional change may occur, which is not preferable.

In order to obtain a film for high-sensitivity heat-sensitive base paper which gives a good perforation with a small amount of heat energy and which has a good curl resistance, which is the most characteristic feature of the present invention, in addition to the above-mentioned film properties, shrinkage properties (heating The balance between shrinkage and heat shrinkage stress is important. That is, the product of the heat shrinkage ratio and the heat shrinkage stress (S
XF) value is 3000-7500, preferably 3500-
It is 7,000. 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. If the S × F value exceeds 7500, curling occurs due to changes in lamination conditions or temperature / humidity during storage, resulting in poor handleability and transportability of the base paper in the stencil printing machine, and problems such as paper jams. It is not preferable because unevenness in thickness, unevenness in density or dimensional change occurs during perforation.

The room temperature curl diameter and the 50 ° C. curl diameter of the film of the present invention are preferably 18 mm or more, more preferably 20 mm or more. Room temperature curl diameter and 50 ° C curl diameter are 1
If it is less than 8 mm, the transportability of the base paper in the stencil printing machine may be poor, and troubles such as paper jam may occur. Furthermore, the ratio of the normal temperature curl diameter to the 50 ° C. curl diameter is preferably 1.0 to 2.0, more preferably 1.0 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 improves the workability during the winding step during film production, the coating during base paper preparation, the laminating step and printing, or prevents fusion between the thermal head and the film during thermal perforation. Therefore, about 10% by weight or less of other polymers (for example, polyethylene, polystyrene,
Polycarbonate, polysulfone, polyphenylene sulfide, polyamide, polyimide, etc.) can be contained. If necessary, additives such as antioxidants, heat stabilizers, lubricants, antistatic agents, dyes and pigments may be added. In particular, in order to achieve the above-mentioned object, it is preferable to roughen the surface of the film to impart appropriate slipperiness to the film, and for that purpose, it is usual to add fine inert particles to the film.

The fine inert particles used in the present invention have an average particle size of 0.05 to 3.0 μm, a particle size distribution value (r) of 1.5 or less, and an average particle size of 0.1 to 2. ．
Those having a particle size distribution value (r) of 0 μm and 1.4 or less are preferable. If the average particle size is less than 0.05 μm, the film winding property tends to 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 heat transfer becomes uneven, resulting in uneven perforation and resolution. May be inferior or the print quality may be impaired.

The amount of the above particles added is preferably 0.05 to 3% by weight, more preferably 0.1 to 2% by weight. If the amount of particles added is less than 0.05% by weight, the winding properties of the film tend to be poor. If the amount of particles added exceeds 3% by weight, the degree of roughening of the film surface tends to be too large, uneven heat transfer occurs, uneven perforation, poor resolution, and poor print quality. There is a risk of damage. 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 crosslinked polymer fine powder as described in JP-A-6 can be mentioned, but it is not limited to these. At this time, the inert particles to be blended may be a single component,
Also, two or more components may be used simultaneously.

In the present invention, the method of blending the inert particles with the polyester 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, to obtain a film whose surface is appropriately roughened by the method as described above, in order to highly satisfy the workability and the resolution during printing, and the printing quality,
The center line average roughness (Ra) of the film surface is 0.02
It is necessary to set it to 0.3 μm, preferably 0.05 to
The range is 0.2 μm. When Ra exceeds 0.3 μm, the degree of roughening of the film surface becomes excessively large, heat transfer becomes uneven, perforation becomes non-uniform, resolution is deteriorated, and print quality is impaired, which is not preferable. On the other hand, when Ra is less than 0.02 μm, the winding property is poor and the workability is deteriorated, which is not preferable. Since the film of the present invention is an extremely thin film, the tensile work modulus in both the longitudinal direction and the width direction of the film is usually 200 kg / mm ² or more, preferably 250 kg / mm ² or more, so that the handling workability and the durability are improved. Printability is further improved.

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.
Alternatively, a liquid coating adhesion method is preferably adopted. The electrostatic application adhesion method is usually a method in which a linear electrode is attached on the upper surface side of the sheet in a direction orthogonal to the flow of the sheet, and the electrode is attached to the electrode in an amount of about 5 to 1
By applying a direct current voltage of 0 kV, a static charge is applied to the sheet to improve the adhesion to the drum. In addition, the liquid application contact method is a method for improving the adhesion between the drum and the sheet by uniformly applying the liquid to the whole or part of the surface of the rotary cooling drum (for example, only the portions that contact both ends of the sheet). Is. In the present invention, both may be used together if necessary.

In the present invention, the stretching conditions for biaxially stretching the thus obtained sheet to form a film will be specifically described. The unstretched sheet is preferably at 20 to 100 ° C. in the longitudinal direction. The film is stretched 2 to 4 times and then 2 to 4 times in the transverse direction to obtain a biaxially oriented film. More preferably, the unstretched sheet is first
2-3 times at 0-80 ° C, 1.1 at 40-100 ° C
~ 1.5 times stretch. At that time, Δn after longitudinal stretching is 0.08.
It is 0 or less, preferably 0.070 or less. 5 in the horizontal direction
The film is stretched 2 to 4 times at 0 to 100 ° C. to obtain a biaxially oriented film. The area ratio of the unstretched sheet is 6
It is also possible to carry out simultaneous biaxial stretching so that the stretching ratio is up to 40 times. The film thus obtained may be heat treated, and if necessary, before and / or after the heat treatment is performed again and / or vertically.
Alternatively, it may be stretched in the transverse direction.

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, and the heat treatment after stretching is not substantially carried out or 110 ° C. or less even if it is carried out. , And below 90 ℃,
The heat treatment time is preferably 1 second to 5 minutes, and the film is preferably stretched or fixed to a length of 30% or less. In addition, according to a conventional method, a predetermined porous thin paper is laminated with a known adhesive to produce a heat-sensitive stencil printing base paper at 40 to 50 ° C.
Curling, which is believed to be due to film shrinkage, may occur during moderate drying processes and during long term storage through the summer months. 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 50 to 60 ° C. for 12 hours to 3 days, the curl resistance in the environment is improved. Will be good.

[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 DSC measurement conditions are as follows. That is, 10 mg of the sample film is used for DSC
Set it in the device and raise the temperature at a rate of 10 ° C / min.
The melting point was measured in the range of 00 ° C, and the melting point was measured as the apex of the melting endothermic peak. (2) Heat shrinkage rate (S) 10 in an oven kept at 100 ° C. in a tensionless state.
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 3) Five points were measured in the longitudinal direction and the transverse direction of the film, and an average value was obtained.

(3) Heat shrinkage stress The film was cut into a strip having 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 chuck distance was set to 50 mm. The film was immersed in an oil bath at 100 ° C. without applying an initial load, and 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) Room temperature curl A Japanese paper made of Manila hemp fiber is used as a support for the film, a vinyl resin is dissolved in toluene as an adhesive, the film and Japanese paper are laminated, and dried in an air oven at 50 ° C for 10 seconds. A heat sensitive stencil sheet was obtained.
The obtained base paper was cut into B4 size, the film surface was placed on a flat table, 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 the time of measurement at room temperature, and the obtained stencil sheet was cut into B4 size, and the film surface was placed on a flat table and the humidity was kept at 50 ° C. The curl diameter after treatment for 1 week in 90% constant temperature and humidity 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.

During Equation 4] particle size distribution value _{(r) = d 25 / d} 75 ( the above formula, d _25, d ₇₅ measures the cumulative volume of the particles from the large particles side, 25% of the respective total volume, 75% (7) Center line average roughness (Ra) It was determined as follows using a surface roughness measuring device (SE-3F) manufactured by Kosaka Laboratory Ltd. That is, a portion having a reference length L (2.5 mm) is extracted from the film cross-section curve in the direction of the center line, and the center line of the extracted portion is taken as the x-axis, and the direction of longitudinal magnification is taken as the y-axis. When represented by f (x), the value given by the following equation was represented by [μm]. The center line average roughness was represented by the average value of the center line average roughness of the extracted portions obtained from the 10 section curves obtained from the surface of the sample film. The tip radius of the stylus was 2 μm, the load was 30 mg, and the cutoff value was 0.08.
mm.

[Equation 5] Ra = (1 / L) ∫ ₀ ^L | f (x) | dx

(8) Practical characteristics of heat-sensitive stencil printing base paper A base paper was prepared by pasting Japanese paper on the film. 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 Δ: Rarely predetermined perforation Is not obtained or there is an area where the size of the perforations is insufficient. X: There are many parts where the prescribed perforations cannot be obtained, the size of the perforations is insufficient, and there is a problem in practical use. 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. ◎: No unevenness in density, no bleeding, clear printing,
Very good ◯: No unevenness in density, bleeding, clear printing, good Δ: Slight unevenness in density, bleeding is slightly observed, and a little lack of sharpness ×: Uneven density, bleeding, or blurring is clearly visible ing

Example 1 (Production of Polyester-A) Dimethyl terephthalate 10
Using 0 parts by weight and 60 parts by weight of ethylene glycol as a starting material, 0.09 parts by weight of magnesium acetate / tetrahydrate as a catalyst was placed in a reactor, the reaction starting temperature was set to 150 ° C., and the reaction temperature was gradually increased with the distillation of methanol. The temperature was raised to 230 ° C. after 3 hours. After 4 hours, the reaction mixture, which had undergone the transesterification reaction substantially, had an average particle size of 1.2.
Ethylene glycol slurry 1 containing 1.0 part by weight of crosslinked organic particles having a particle size distribution value (r) of 1 μm and 1.2
0 parts by weight of ethyl acid phosphate was added.
04 parts and 0.04 parts of antimony trioxide were added and 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 was gradually reduced from the normal pressure to finally set it to 0.3 mmHg. After starting the reaction
After 4 hours, the reaction was stopped and the polymer was discharged under nitrogen pressure. The intrinsic viscosity of the obtained polyester is 0.
The melting point was 75 and the melting point was 257 ° C.

(Production of Polyester-B) 100 parts by weight of dimethyl terephthalate, 56 parts by weight of 1,4-butanediol and 0.005 parts by weight of tetrabutyl titanate were placed in a reactor and the reaction starting temperature was set to 150 ° C. The reaction temperature was gradually raised with the evaporation, and after 3 hours, 21
It was set to 0 ° C. After 4 hours, tetrabutyl titanate 0.0
After adding 05 parts by weight, a polycondensation reaction was carried out for 4 hours. That is, the temperature was gradually raised from 210 ° C to 260 ° C. On the other hand, the pressure gradually decreases from atmospheric pressure and finally becomes 0.3
It was mmHg. After 4 hours from the start of the reaction, the reaction was stopped and the polymer was discharged under nitrogen pressure. The obtained polyester has an intrinsic viscosity of 0.90 and a melting point of 230 ° C.
Met. (Production of Polyester-C) Production of Polyester-A except that 60 parts by weight of dimethyl terephthalate and 40 parts by weight of dimethyl isophthalate were used in place of 100 parts by weight of dimethyl terephthalate in Production of Polyester-A and no crosslinked organic particles were added. Polyester-C was obtained in the same manner as in. The obtained polyester had an intrinsic viscosity of 0.73 and a melting point of 151 ° C.

(Production of Polyester-D) In Production of Polyester-A, 54 parts by weight of ethylene glycol instead of 60 parts by weight of ethylene glycol, 5.6 parts by weight of 1,4 butanediol, average particle size of 1.21 μm, particle size Polyester-D was obtained in the same manner as in Polyester Production-A, except that the cross-linked organic particles having a distribution value (r) of 1.2 were 0.5 parts by weight. The obtained polyester had an intrinsic viscosity of 0.75 and a melting point of 235 ° C.

(Production of Polyester-E) The same as Production-A of polyester except that instead of 100 parts by weight of dimethyl terephthalate in Preparation of polyester-A, 85 parts by weight of dimethyl terephthalate and 15 parts by weight of dimethyl isophthalate are used. Polyester-E was obtained by the method. The obtained polyester has an intrinsic viscosity of 0.72 and a melting point of 215 ° C.
Met. (Production of Polyester-F) Production of Polyester-A except that 85 parts by weight of dimethyl terephthalate and 15 parts by weight of dimethyl isophthalate were used in place of 100 parts by weight of dimethyl terephthalate in Production of Polyester-A, and no crosslinked organic particles were added. Polyester-F was obtained by the same method as described above. The obtained polyester had an intrinsic viscosity of 0.72 and a melting point of 215 ° C.

(Production of Polyester Film) 50 parts by weight of polyester-F and 50 parts by weight of polyester-B were uniformly blended, melt-kneaded at 265 ° C. by a twin-screw extruder, and extruded into chips. The melting point of the obtained blended polyester was 216 ° C and 222 ° C. The melting point of the polyester is 219 ° C. on average, and the polyester (a)
And Polyester-B 10 parts by weight as polyester (b) was uniformly blended with 90 parts by weight of polyester (a) and extruded into a sheet at 265 ° C., and the surface temperature was 3
A rotating cooling drum set at 0 ° C. was used to rapidly cool and solidify by using an electrostatic applied cooling method to obtain a substantially amorphous sheet having a thickness of 13.5 μm. The obtained sheet was stretched in the machine direction at 65 ° C. for 2.5 times, further at 75 ° C. for 1.2 times, then in the transverse direction at 80 ° C. for 3.0 times, and then heat treated at 90 ° C. for 6 seconds. Then, a biaxially oriented film having a thickness of 1.5 μm was manufactured. 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 printing base paper was prepared in the same manner as in Example 1 except that the polyester (a) was changed to 90 parts by weight as polyester (a), and was imprinted. Example 3 A thermal stencil printing base paper was prepared in the same manner as in Example 1 except that 90 parts by weight of polyester-F was used as the polyester (a), and was imprinted.

Comparative Example 1 In Example 1, 100 parts by weight of polyester-A was used as polyester (a), polyester (b) was not used, the extruder temperature was 280 ° C., and the obtained sheet was 80 ° C. in the longitudinal direction. In the same manner as in Example 1 except that the sheet is stretched 3.0 times in the transverse direction at a rate of 3.0 times at 90 ° C., and then heat treated at 210 ° C. for 6 seconds to prepare a stencil sheet for thermal stencil printing. I went. Comparative Example 2 A heat-sensitive stencil printing base paper was prepared in the same manner as in Example 1 except that the polyester-E was 10 parts by weight as the polyester (b), and was imprinted.

Comparative Example 3 A heat sensitive stencil was prepared in the same manner as in Comparative Example 1 except that 97 parts by weight of polyester-A was used as the polyester (a) and 3 parts by weight of polyester-C was used as the polyester (b). We made a base paper for printing and printed it. Comparative Example 4 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 stencil printing was performed. Comparative Example 5 A heat-sensitive stencil printing base paper was prepared in the same manner as in Example 1 except that the heat treatment was performed at 140 ° C. for 6 seconds.
Photographed and printed. The results obtained above are summarized in Tables 1 and 2 below.

[0032]

[Table 1]

[0033]

[Table 2]

[0034]

According to the film of the present invention, the perforation sensitivity,
A film for high-sensitivity heat-sensitive stencil sheet having excellent printing resolution and curl resistance can be provided, and its industrial value is high.

Claims (1)

[Claims] 1. A polyester resin (a) having a melting point of 200 to 260 ° C. of 70 to 95% by weight and a melting point of 100 to 200 ° C.
Is a biaxially stretched film having a thickness of 0.5 to 5 μm obtained from a mixture with 5 to 30% by weight of the polyester resin (b), characterized in that the following formulas (1) to (5) are simultaneously satisfied. Film for high-sensitivity heat-sensitive stencil printing base paper. ## EQU1 ## 30 ≦ ΔTm ≦ 150 (1) 16 ≦ S ≦ 40 (2) 80 ≦ F ≦ 270 (3) 3000 ≦ S × F ≦ 7500 (4) 0.02 ≦ Ra ≦ 0.3 (5) (where ΔTm is the difference (° C.) between the melting points of the polyester resin (a) and the polyester resin (b), and S is 1 at 100 ° C.
Heat shrinkage (%) after treatment for 0 minutes, F is 10 at 100 ° C
Heat shrinkage stress (g / mm ² ) after treatment for seconds, Ra represents center line average roughness (μm))