JP3481995B2 - High-sensitivity heat-sensitive stencil film for base paper - Google Patents

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 high-sensitivity, heat-sensitive stencil sheet for stencil sheet, which has excellent perforation sensitivity and excellent printing properties such as 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) The thermal perforation sensitivity is good. That is, it must have a sufficient heat shrinkage ratio that it can be melted with a small amount of heat and that a perforation of an appropriate size can be obtained so that an image at the time of printing becomes clear. (2) It should have strength and elastic modulus sufficient to withstand the work of laminating with porous thin paper and printing. Also, in such work, even if there is a heating step, the problem such as a remarkable curl of the base paper does not occur due to the influence of the heating step. (3) The 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.

In addition to these requirements, it is also required to be excellent in handleability and productivity during film production and base paper production. Specifically, during film production,
Stretchability is good, troubles such as breakage do not occur, and
It is necessary to have good winding and slitting properties, and to prevent wrinkles and winding misalignment during winding. 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. 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. 63-227
No. 634) or a film having a specified heat shrinkage property (Japanese Patent Laid-Open No. 62-282983, Japanese Patent Laid-Open No. 63-1).
No. 60895, Japanese Patent Laid-Open No. 63-321192,
Japanese Laid-Open Patent Publication No. 3-30996) and the like have been proposed.
Not all of the above problems could be solved.

[0004]

DISCLOSURE OF THE INVENTION As a result of intensive studies in view of the above problems, the present inventors have made a biaxially oriented film made of polyester having a specific composition and having shrinkage and heat shrinkage stress satisfying specific conditions. However, they have found that they are suitable for use as heat-sensitive stencil printing base paper, and have completed the present invention.

That is, the gist of the present invention is a biaxially oriented film having a thickness of 0.5 to 6.0 μm, comprising a polyester composition containing 20 to 80% by weight of polybutylene terephthalate, and having a thickness of 60 to 140 ° C. The maximum value of the average value of the heat shrinkage stress of the film in the longitudinal direction and the transverse direction of the film exceeds 300 g / mm ² , the heat shrinkage rate after treatment at 100 ° C. for 3 minutes is 20% or more, and the melting endothermic peak is occur more than two places state, and are difference 5 ° C. or more of the melting endotherm temperature,
A high-sensitivity, heat-sensitive stencil printing base paper film is characterized by simultaneously satisfying the following formulas (1) and (2) .

The present invention will be described in detail below. The polybutylene terephthalate (PBT) referred to in the present invention means 70 mol% or more, preferably 80 mol% of the dicarboxylic acid component.
The above refers to a polyester in which 50 mol% or more, preferably 70 mol% or more of terephthalic acid and glycol components are 1,4-butanediol. In addition, PB in the present invention
The polyester composition containing 20 to 80% by weight of T means a composition containing PBT and one or more polyesters other than PBT. What is polyester here?
It refers to a polyester composed of a dicarboxylic acid component such as terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, and a glycol component such as ethylene glycol, but may be a copolymer containing other components. As such a copolymerizable component, in addition to the above components,
Dicarboxylic acids such as phthalic acid, sebacic acid, adipic acid,
Examples thereof include diethylene glycol, triethylene glycol, a polyol component, and oxycarboxylic acid such as p-hydroxybenzoic acid.

As a method of obtaining such a polyester composition, a method of blending PBT and another polyester and melt-kneading is preferably used. The content of PBT in the present invention is preferably 30 to 80% by weight, more preferably 40 to 70% by weight. When it is 20% by weight or less, the shrinkage property for obtaining a high perforation sensitivity cannot be obtained, which is not preferable. On the other hand, if it exceeds 80% by weight, the stretchability is remarkably deteriorated during the production of the film and the productivity is lowered, which is not preferable. The melting point of the polyester of the present invention is 150 to 2 when formed into a film.
It is preferably in the range of 40 ° C, and more preferably in the range of 160 to 230 ° C. If the melting point is higher than 240 ° C, high perforation sensitivity may not be obtained, and if the melting point is lower than 150 ° C, the heat-resistant dimensional stability of the film deteriorates and the curl is produced during the process of manufacturing the base paper or during storage of the base paper. May occur, or the gradation of the printed image may be poor.

The melting point is measured by DSC (differential calorimetry), but it is preferable to obtain melting endothermic peaks at two or more points in order to obtain higher perforation sensitivity. The difference between the melting endothermic temperatures is preferably 5 ° C. or higher, more preferably 10 ° C. or higher. In such a case, in the present invention, when the energy calculated from the lowest temperature peak (I) is 30% or more of the total energy calculated from all the melting peaks, the temperature at the peak of the peak (I) Is the melting point, and when it is less than 30%, the temperature at the apex of the peak with the largest melting energy is the melting point.

In the present invention, it is necessary that the maximum value of the average value in the longitudinal and transverse directions of the heat shrinkage stress of the film in the range of 60 to 140 ° C. exceeds 300 g / mm ² .
If it is 300 g / mm ² or less, the force for expanding the holes at the time of perforation is insufficient, and perforations having a size sufficient to obtain a clear image at the time of printing cannot be obtained, which is not preferable.
The maximum value of the heat shrinkage stress is preferably 500 to 15
00 g / mm ² , more preferably 550 to 1300 k
It is g / mm ² . In the present invention, it is preferable that the following equations (1) and (2) are simultaneously satisfied, where Sm is the heat shrinkage stress in the longitudinal direction of the film at 100 ° C. and St is the heat shrinkage stress in the lateral direction. .

[Equation 3] (Sm + St) / 2 ≧ 300 g / mm²  …… (1) 1.2 ≦ Sm / St ≦ 5 (2) (In the above formula, Sm is the longitudinal direction of the film at a temperature of 100 ° C.
Heat shrinkage stress (g / mm ²), St is the fill at the same temperature
Lateral heat shrinkage stress (g / mm²))

When the average value of the heat shrinkage stress of the film in the vertical and horizontal directions ((Sm + St) / 2) is less than 300 g / mm ² ,
In some cases, the force for expanding the holes during punching may be insufficient, and it may not be possible to obtain punches having a size large enough to obtain a clear image during printing. The average value of such heat shrinkage stress is preferably 500 to 1500 g / mm ² , and more preferably 550 to 1300 kg / mm ² .

The ratio (Sm / St) of heat shrinkage stress in the machine direction to the machine direction in the machine direction is preferably 1.2 to 5, more preferably 1.5 to 3.5. When the value of this ratio is less than 1.2, that is, when the heat shrinkage stress in the longitudinal direction is not large, the perforation sensitivity and printing durability during printing may be poor. On the other hand, when Sm / St exceeds 5, the uniformity of the perforated shape is deteriorated, and the image density and resolution during printing may be poor. In addition to these requirements, in the present invention, the shrinkage rate of the film after treatment at 100 ° C. for 3 minutes needs to be 20% or more, preferably 30 to 80%. If it is less than 20%, the perforation sensitivity is insufficient and the print-like image density is lowered, which is not preferable.

The film of the present invention is used to improve workability during winding process during film production, coating process during base paper preparation, laminating process and printing, or fusion between the thermal head and film during thermal perforation. In order to prevent the above, it is desirable to roughen the surface to impart appropriate slipperiness to the film, and in order to appropriately roughen the surface, fine particles having an average particle size of 0.05 to 2.0 μm are usually used. 0.01 to 2.0% by weight, preferably 0.1 to 1.5% by weight. Examples of such fine particles include 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. Examples thereof include black, silicon nitride, boron nitride, and crosslinked polymer fine powders described in JP-B-59-5216, but are not limited thereto. At this time, the fine particles to be mixed may be a single component, or two or more components may be used at the same time. When two or more components are used, it is preferable that the total average particle size and content of them are within the ranges described above. The average particle size is less than 0.05 μm, or the content of fine particles is 0.0
If it is less than 1% by weight, roughening of the film surface may be insufficient and sufficient effects may not be obtained. When the average particle size exceeds 2.0 μm or the content exceeds 2.0% by weight, the degree of roughening of the film surface is too large and uneven heat transfer occurs, resulting in uneven perforation. Therefore, the resolution may be inferior or the print quality may be impaired.

A particularly preferred method for roughening the surface of the film is a particle (A) having an average particle size (d ₁ ) of 0.6 to 3.0 μm and a Mohs hardness of 5 or more and an average particle size (d ₂ ) of 0. 06 ~
This is a method in which particles (B) having a particle size of 0.8 μm and d ₁ / d _{2 of 2} to 10 are contained. The mechanism by which particles having a high Mohs hardness give good results for the thermal head stain is not clear, but particles having a hardness equal to or higher than that of the thermal head have a remarkable effect and thus form film surface protrusions. It is considered that the cleaning effect can be obtained by polishing the head together with the dirt that the particles adhere to the thermal head.

When the Mohs hardness of the particles (A) used in the present invention is less than 5, dirt adheres to the thermal head during plate making many times,
Perforation sensitivity may be reduced. If the average particle size of the particles (A) is less than 0.6 μm, the winding property may be poor. When the average particle size of the particles (A) exceeds 3.0 μ, the flatness of the film surface is impaired and uneven heat transfer occurs.
Perforations may be uneven, resulting in poor resolution and impaired print quality. When the average particle diameter of the particles (B) is less than 0.06 μm, slipperiness may be insufficient and workability may be reduced. When it exceeds 0.8 μm, the flatness of the film surface is impaired and heat transfer becomes uneven. May occur, resulting in uneven perforation, poor resolution, and impaired print quality.

[0015] The ratio of the average particle sizes of (d ₁₎ and the particles of inert particles (A) (B) (d 2) (d 1 / d 2) 2
When it is in the range of 10 to 10, the associated air layer at the time of winding the film can be rapidly reduced, and good film winding characteristics can be enjoyed. Further, if d ₁ / d ₂ exceeds 10, the degree of roughening of the film surface is too large, uneven heat transfer occurs, uneven perforation, poor resolution, and impaired print quality. There is.

The Mohs hardness of the particles (A) used in the present invention is preferably 5.5 or more, and the average particle diameter of the particles (A) is 0.8.
The average particle size of the particles (B) is more preferably 0.1 to 0.6 μm. The number of particles in 1 g of the polyester resin is usually 8.85 × 10 ^{5 to} 1.33 as described above for the film of the particles (A).
× 10 a ¹⁰ range, more addition amount 0.01 to 0.2% by weight of the film, the range number 1.77 × 10 ⁶ ~8.84 × 10 ⁹ pieces in the polyester resin 1g particles Is preferred. If the amount of the particles (A) added to the film is less than the above range, the film winding property may be poor. Also,
When the amount of addition or the number of particles exceeds the above range, the degree of roughening of the film surface is too large, resulting in uneven heat transfer,
Perforations may be uneven, resulting in poor resolution and impaired print quality.

The content of the particles (B) is as described above, but the number of particles in 1 g of the polyester resin is usually 4.6.
The range is 7 × 10 ^{8 to} 2.65 × 10 ¹⁴ , and the addition amount is 0.1 to 2% by weight and the number of particles is 9.33 × 10.
The range of ^{8 to} 1.77 × 10 ¹⁴ is preferable. Particle (B)
When the content and the number of particles are less than the above range, slipperiness may be insufficient and workability may be deteriorated. When the content of the particles (B) and the number of particles exceed the above ranges, the flatness of the film surface is impaired, heat transfer becomes uneven, and the same inconvenience as described above may occur.

Examples of the inert particles (A) having a Mohs hardness of 5 or more used in the present invention include silicon oxide, titanium oxide, zeolite, silicon nitride, boron nitride, celite, alumina, and the like. It is not limited. In the present invention, by the method as described above, it is preferable to obtain a film whose surface is appropriately roughened, but prevents the decrease in sensitivity due to the melted portion of the film adhering to the thermal head during perforation, In addition, in order to further satisfy the resolution and printing quality during printing, it is preferable to use fine particles having a sharp particle size distribution. That is, in the particle size distribution measured by the method described below, d ₂₅ / d ₇₅ is preferably 1.0 to 1.5, more preferably 1.1 to 1.3. If d ₂₅ / d ₇₅ exceeds 1.5, protrusions with a large spread tend to increase. From this viewpoint, as the particles to be contained in the film, one or more selected from spherical silica, synthetic calcium carbonate, and monodisperse crosslinked polymer fine powder as described in JP-A-2-194049 are used. Is most preferred. The method of incorporating particles into the film is preferably a method of adding to the polymerization step of polyester or a method of melt-kneading before forming into a film.

In the present invention, a film whose surface is appropriately roughened by the above-mentioned method is obtained, but in order to further satisfy workability, resolution during printing, and print quality, the film surface is The center line average roughness (Ra) is preferably 0.01 to 0.4 μm, more preferably 0.02 to 0.3 μm, and the maximum height (Rt) of the film surface is 0. The thickness is preferably 4 to 3 μm, more preferably 0.5 to 2 μm, and it is desirable to appropriately select the conditions so as to fall within this range.

The thickness of the film of the present invention is 0.5 to 6 μm.
m, preferably 0.8 to 3 μm. The thinner the film is, the shorter the heat conduction distance is. As a result, the thermal energy required at the time of perforation is reduced, the perforation property is improved, and the printing quality is improved. However, when the film thickness is less than 0.5 μm, the printing is unclear, uneven density is likely to occur, and the printing durability is deteriorated. When the film thickness exceeds 5 μm, unevenness occurs during printing. 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 /
When it is at least ² mm ² , preferably at least 350 kg / mm ² , handling workability and printing durability will be 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 necessary to enhance the adhesion between the sheet and the rotary cooling drum, and the electrostatic application adhesion method and / or the liquid coating adhesion method are preferably adopted in the present invention.

The electrostatic application adhesion method is usually a method in which a linear electrode is placed on the upper surface of the sheet in a direction orthogonal to the flow of the sheet, and a DC voltage of about 5 to 10 kV is applied to the electrode to statically apply the sheet. This is a method of applying an electric charge 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 sheet thus obtained is usually biaxially stretched to form a film.
Describing the stretching conditions specifically, the unstretched sheet is preferably 20 to 100 ° C., more preferably 25 to 100 ° C.
In the temperature range of 80 ° C., first, in one direction, by a roll or tenter type stretching machine, 3.0 to 7 times, preferably 3.
Stretch 5 to 7 times. Next, it is preferably 20 to 100 ° C, more preferably 25 to 90 ° C in the direction orthogonal to the first stage.
In the temperature range of 3.0 to 7 times, preferably 3.5 to 7 times,
More preferably, the film is stretched 4.0 to 7 times to obtain a biaxially oriented film. A method in which unidirectional stretching is performed in two or more stages can be used, but in that case as well, it is desirable that the final stretching ratio falls within the above range. It is also possible to simultaneously biaxially stretch the unstretched sheet so that the area ratio becomes 10 to 40 times. The film thus obtained may be heat-treated, and if necessary, may be stretched 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 15 times or more as an area ratio, and the heat treatment after stretching is not substantially performed or 110 ° C. or less even if it is performed, and further, 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.

In the present invention, about 10% by weight or less of another polymer (for example, polyethylene, polystyrene, polycarbonate, polysulfone, polyphenylene sulfide, polyamide, polyimide, etc.) is contained with respect to the total amount of polyester used for film formation. You can
Further, if necessary, additives such as an antioxidant, a heat stabilizer, a lubricant, an antistatic agent, a dye and a pigment may be added. Thus obtained polyester film of the present invention, by laminating a predetermined porous thin paper using a known adhesive according to a conventional method, has excellent thermal piercing property, and the resolution and gradation during printing. A heat-sensitive stencil printing base paper having excellent properties can be obtained.

[0025]

EXAMPLES The present invention will be described in more detail below with reference to examples.
As will be understood, the present invention is as follows unless the gist thereof is exceeded.
It is not limited to the examples. Used in the present invention
The methods for measuring physical properties are shown below. (1) Intrinsic viscosity 1 g of polymer was added to phenol / tetrachloroethane (50
/ 50 (weight ratio))
And measured with an Everode viscometer at 30 ° C. (2) Average particle size of fine particles Shimadzu Corporation Centrifugal Sedimentation Type Particle Size Analyzer SA-
For the sedimentation method based on Stokes' resistance law using CP3 type
Therefore, the size of the particles was measured. Grains obtained by measurement
50% cumulative (weight basis) in the equivalent spherical distribution of the child
Average particle size (d₅₀). Similarly, on the large particle side
25% value from d_{twenty five}, 75% value is d ₇₅And

(3) Film thickness The thickness was measured using a thickness meter, Mumetron, made by Citizen Watch. (4) 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 was set in the DSC apparatus, the temperature was raised at a rate of 10 ° C / min, and 0 ° C to 3
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. (5) Vertical and Horizontal Average Heat Shrinkage The sample was heat-treated in an oven kept at 100 ° C. in a tensionless state for 3 minutes, the length of the sample before and after the heat treatment was measured, and the heat shrinkage was calculated by the following formula.

[0027]

[Equation 4] Five points were measured in the longitudinal direction and the transverse direction of the film, and an average value was obtained.

(6) Heat shrinkage stress Cut the film into strips with a width of 10 mm and load one end
Set to the detector chuck and the other to the fixed chuck
The distance between the chucks was 50 mm. Do not apply initial load
In that state, immerse the film in an oil bath at a predetermined temperature,
The stress value was measured 5 seconds after the start of immersion. Before soaking
Rum cross-sectional area to heat shrinkage stress (g / mm ²) Is calculated
It was Measured at 5 points in the film lengthwise and widthwise directions, and averaged
I asked. Measurement is in the range of 60 ℃ -140 ℃ every 10 ℃
The maximum of the measured values at the 9 points.
The maximum value.

(7) Center Line Average Roughness (Ra) It was determined as follows using a surface roughness measuring instrument (SE-3F) manufactured by Kosaka Laboratory Ltd. That is, the reference length L (2.55 mm) from the film section curve in the direction of the center line
The part of is drawn out, and the center line of this extracted part is the x-axis,
When the roughness curve y = f (x) is represented with the direction of the longitudinal magnification as the y-axis, the value given by the following formula is 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 mmg, and the cutoff value was 0.0.
It was 8 mm.

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

(8) Maximum Height (Rt) The center line average roughness was measured, and the extracted part was sandwiched by two straight lines parallel to the center line of the extracted part (2.5 mm) of the cross-section curve obtained. At this time, the distance between these two straight lines was measured in the direction of the longitudinal magnification of the sectional curve, and the value was taken as the maximum height (μm) of the extracted portion. The maximum height was obtained by calculating 10 cross-section curves from the surface of the sample film and expressing the average value of the maximum heights of the extracted portions obtained from these cross-section curves.

(9) Thermosensitive stencil printing base paper Practical properties Washi paper was attached to the film to prepare a 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. (I) Perforation sensitivity ◯: Predetermined perforation was reliably performed, and the size of perforation was sufficient, which was good. Δ: Practical use is possible, although there are rarely parts where the desired perforation cannot be obtained or parts where the perforation size is insufficient. X: There are many portions where the predetermined perforation cannot be obtained, and the perforation size is insufficient, which is a practical problem. Moreover, the following characteristics were visually determined for the characters and images obtained by actually printing using a lithographic base paper and a lithograph AP7200 printing machine manufactured by Ideal Science Co., Ltd.

(Ii) Printing quality: Good; clear printing is possible without uneven density and bleeding. Δ: Slight unevenness in shades and bleeding were observed, and the image was slightly lacking in sharpness. ×: The unevenness of light and shade, bleeding, and blurring are clearly seen. (Iii) Printing durability ◯ ... Image density and resolution do not change even after printing 2000 sheets or more. △ ... Image bleeding is slightly recognized after printing about 1000 sheets. X ... Image bleeding after printing several hundred sheets. (10) Rolling characteristics A film produced at a line speed of about 170 m / min is wound up to 6000 m on a paper tube with a diameter of 15 cm, and the state of the end face is observed, and evaluated according to the following 3 rank criteria. did. ◎ ... The end faces are all aligned 〇 ... The end faces are almost aligned and can be used △: A part of the end faces is irregular × ... The lower part of the end faces is irregular

Example 1 100 parts dimethyl terephthalate, 56 parts 1,4-butanediol, and 0.0075 tetrabutyl titanate.
Part of the mixture was placed in a reactor, the reaction starting temperature was set to 150 ° C., the reaction temperature was gradually raised as methanol was distilled off, and the temperature was raised to 210 ° C. after 3 hours. Furthermore, after the reaction was carried out for 1 hour, a polycondensation reaction was carried out by a conventional method. In this reaction, the temperature is gradually raised and the pressure is gradually reduced from normal pressure,
After hours, the temperature was 260 ° C. and the pressure was 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 PBT was 0.90. Also, 100 parts of dimethyl terephthalate and 60 parts of ethylene glycol were used as starting materials, and 0.09 part of magnesium acetate / tetrahydrate as a catalyst was added to carry out a transesterification reaction.

Then, the average particle size is 1.1 μm, and d ₂₅ / d ₇₅
Spherical silica particles of 1.2 are added as an ethylene glycol slurry to give ethyl acid phosphate 0.0
4 parts and 0.04 part of antimony trioxide were added and polycondensation reaction was carried out for 4 hours to obtain polyethylene terephthalate A. The intrinsic viscosity of the polyester was 0.65, and the content of spherical silica particles in the polymer was 0.7% by weight. 50 parts of the obtained polyester A and 50 parts of PBT are mixed, extruded in a sheet form from an extruder at 280 ° C., and rapidly cooled and solidified by a static cooling method using a rotary cooling drum whose surface temperature is set to 20 ° C. Thus, a substantially amorphous sheet having a thickness of 32 μm was obtained. Then, the obtained sheet was stretched in the longitudinal direction by 4.3 times at 65 ° C. and in the transverse direction at 70 ° C. by 4.6 times and further heat-treated at 90 ° C. for 6 seconds to give a biaxially oriented film of 2.0 μm in thickness. Was manufactured.

Example 2 80 mol% of the acid component is terephthalic acid, 20 mol% is isophthalic acid, and the glycol component is ethylene glycol. A polyethylene terephthalate / isophthalate copolymer B having an intrinsic viscosity of 0.68 was produced. The copolymer B
Contained 0.7% by weight of monodisperse crosslinked polymer particles (main component styrene and divinylbenzene) having an average particle size of 0.6 μm and ad ₂₅ / d ₇₅ of 1.25. A mixture of 45 parts of PBT produced in Example 1 and 55 parts of copolymer B was used as a raw material and a substantially amorphous sheet having a thickness of 35 μm was obtained in the same manner as in Example 1. The obtained sheet was stretched 4.2 times in the longitudinal direction and 4.5 times in the transverse direction at 60 ° C., and heat-treated at 85 ° C. for 6 seconds under a constant length to obtain a biaxial orientation of 2.0 μm in thickness. I got a film. Example 3 A mixture of 70 parts of PBT produced in Example 1 and 30 parts of copolymer B was used as a raw material in the same manner as in Example 1 to obtain a substantially amorphous sheet having a thickness of 40 μm. The obtained sheet is simultaneously biaxially stretched at 70 ° C. to 4.5 × 4.5 times, and heat-treated at 95 ° C. for 30 seconds under a constant length to obtain a biaxially oriented film having a thickness of 2.2 μm. It was

Comparative Example 1 The heat treatment temperature was 140 ° C., and 10% in the width direction during the heat treatment.
A biaxially oriented film having a thickness of 2.0 μm was obtained in the same manner as in Example 1 except that the relaxation was performed. Comparative Example 2 A biaxially oriented film was obtained in the same manner as in Example 1 except that the polymer extrusion rate was adjusted to a thickness of 6.0 μm.

Comparative Example 3 A thickness of 2 was obtained in the same manner as in Example 1 except that the mixing ratio of the raw materials was 15 parts of PBT and 85 parts of polyethylene terephthalate A, and the stretching temperature was 85 ° C. and 100 ° C. A biaxially oriented film of 0.0 μm was obtained. Comparative Example 4 Example 1 except that the mixing ratio of the raw materials in Example 1 was 85 parts PBT and 15 parts polyethylene terephthalate A.
I tried to produce a biaxially oriented film in the same manner as
The stretchability was poor and the film was frequently broken, and a satisfactory film could not be obtained. The film thus obtained 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. The physical properties of the film and the printing characteristics are shown in Table 1 below.
And 2 collectively.

[0038]

[Table 1]

[0039]

[Table 2]

The films of Examples 1 to 3 are excellent in handleability at the time of producing the film and at the time of making the base paper, and the base papers made by using them are excellent in thermal perforation sensitivity, and thus show good copy printing characteristics. It was a thing. On the other hand, in Comparative Example 1, the shrinkage stress was insufficient, and in Comparative Example 2, the thickness was too thick. In Comparative Example 3, PBT was not contained in a predetermined amount. .

Example 4 90 parts of dimethyl terephthalate and dimethyl 1 isophthalate
Using 0 parts and 60 parts of ethylene glycol as starting materials, 0.09 parts of magnesium acetate / tetrahydrate as a catalyst was added,
A transesterification reaction was performed. Then average particle size 1.1μ
m, d ₂₅ / d ₇₅ spherical silica of 1.2 was added as ethylene glycol slurry, 0.04 part of ethyl acid phosphate and 0.04 part of antimony trioxide were added, and polycondensation reaction was carried out for 4 hours, polyethylene Nterefuta
A rate / isophthalate copolymer C was obtained. The Poles
The intrinsic viscosity of tellur is 0.67, and it is spherical in the polymer.
The content of silica particles was 1.0% by weight. 50 parts of the obtained polyester C and PBT5 produced in Example 1
0 parts were mixed, extruded into a sheet form from an extruder at 280 ° C., rapidly cooled and solidified by using an electrostatic applied cooling method in a rotary cooling drum whose surface temperature was set to 20 ° C., and substantially 32 μm in thickness. An amorphous sheet was obtained. Then, the obtained sheet was stretched 4.5 times at 60 ° C. in the longitudinal direction and 4.0 at 70 ° C. in the lateral direction.
The film was stretched twice and further heat-treated at 90 ° C. for 6 seconds to produce a biaxially oriented film having a thickness of 1.9 μm .

Comparative Example 5 In the same manner as in the case of PBT produced in Example 1, PBT copolymer C was prepared from 80 parts of dimethyl terephthalate, 20 parts of dimethyl isophthalate and 56 parts of 1,4-butanediol as raw materials. Manufactured. The obtained polymer had an average particle size of 0.
0.4 wt% of 6 μm, synthetic calcium carbonate having ad ₂₅ / d ₇₅ of 1.45 was compounded using a twin-screw extruder. The intrinsic viscosity of the obtained particle-containing polymer was 0.85. Using the polymer, a thickness of 2.2 was obtained in the same manner as in Example 1.
A biaxially oriented film of μm was obtained. The film thus obtained 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. The physical properties and the imprinting characteristics of the film are summarized in Tables 3 and 4 below.

[0043]

[Table 3]

[0044]

[Table 4]

The films of Examples 4 and 5 are excellent in handleability at the time of producing the film and at the time of making the base paper, and the base paper made by using them has excellent thermal perforation sensitivity, and thus shows good copy printing characteristics. It was a thing. Examples 5 to 8 and Comparative Examples 6 and 7 (Production of Polyester-1) Dimethyl terephthalate 80
Parts by weight, 20 parts by weight of dimethyl isophthalate and 60 parts by weight of ethylene glycol are used as starting materials, and 0.09 parts by weight of magnesium acetate / tetrahydrate as a catalyst is placed in a reactor,
The reaction start temperature was set to 150 ° C., and the reaction temperature was gradually raised as the methanol was distilled off, and the temperature was set to 230 ° C. after 3 hours. After 4 hours, an ethylene glycol slurry containing 0.6 parts by weight of organic particles having an average particle size of 0.35 μm and a particle size distribution value (r) of 1.4, was added to the reaction mixture in which the transesterification reaction was substantially completed. 10 parts by weight were added, 0.04 part of ethyl acid phosphate and 0.04 part of antimony trioxide were added, and polycondensation reaction was carried out for 4 hours. That is, the temperature is gradually raised from 230 ° C. to 280 ° C.,
The pressure was gradually reduced from normal pressure to finally set to 0.3 mmHg. After 4 hours from the start of the reaction, the reaction is stopped,
The polymer was discharged under nitrogen pressure. The intrinsic viscosity of the obtained polyester was 0.72. This polyester was designated as polyester E. Polyester I was produced by the same method, and its composition is shown in Table 5 below.

(Production of Polyester-2) 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 start temperature was set to 150 ° C. The reaction temperature was gradually increased as the solvent was distilled off, and the temperature was adjusted to 210 ° C. after 3 hours. After 4 hours, the transesterification reaction was substantially completed and the reaction mixture had an average particle size of 1.0 μm and d ₂₅
10 parts by weight of a 1,4-butanediol slurry containing 0.1 part by weight of spherical silica particles having a / d ₇₅ of 1.2 was added. Further, 0.005 parts by weight of tetrabutyl titanate was added as a polymerization catalyst, and polycondensation reaction was carried out by a conventional method. That is, the temperature is gradually raised from 210 ° C. to 260
℃, the pressure is gradually reduced from normal pressure and finally 0.3 m
It was set to mHg. 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. This polyester was designated as polyester F. Polyester G, polyester H, polyester J, and polyester K were produced in the same manner, and their compositions are as shown in Table 5.

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[Table 5]

(Manufacture of Film) Various polyesters shown in Table 6 below were used to extrude a sheet at 280 ° C. from an extruder, and a static cooling method was applied using a rotary cooling drum whose surface temperature was set to 30 ° C. And rapidly solidify to a thickness of 32μ
A substantially amorphous sheet of m was obtained. The obtained sheet was stretched 4.5 times in the longitudinal direction at 65 ° C. and 4.3 times in the transverse direction at 70 ° C., and further heat treated at 90 ° C. for 6 seconds to obtain a biaxially oriented film having a thickness of 1.5 μm. Manufactured. 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. The physical properties of the film and the practical properties of the base paper are shown in Tables 6 to 8 below.

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[Table 6]

[0050]

[Table 7]

[0051]

[Table 8]

[0052]

EFFECT OF THE INVENTION The polyester film of the present invention has good handleability, and the heat-sensitive stencil printing base paper using the film is excellent in heat perforation, resolution at printing and print quality. Industrial value is high.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-2-158391 (JP, A) JP-A-3-182395 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B41N 1/24 102

Claims (3)

(57) [Claims] 1. Polybutylene terephthalate 20 to 8
A biaxially oriented film having a thickness of 0.5 to 6.0 μm, which comprises a polyester composition containing 0% by weight, and is 60
The maximum value of the average value of the heat shrinkage stress of the film in the longitudinal direction and the transverse direction of the film in the range of up to 140 ° C exceeds 300 g / mm ^2, and the thermal shrinkage rate after the treatment at 100 ° C for 3 minutes is 20% or more, melting endothermic peak exists over two places state, and are difference 5 ° C. or more of the melting endotherm temperature, the following formula (1) and (2)
A film for high-sensitivity heat-sensitive stencil printing base paper, which is characterized by simultaneously satisfying (1) (Sm + St) / 2 ≧ 300 (1) 1.2 ≦ Sm / St ≦ 5 (2) (In the above formula, Sm is the heat shrinkage stress in the machine direction of the film at a temperature of 100 ° C. ( g / mm ² ) and St represent heat shrinkage stress (g / mm ² ) in the transverse direction of the film at the same temperature) 2. The film for high-sensitivity heat-sensitive stencil printing base paper according to claim 1, which has a melting point of 150 to 240 ° C. 3. A Mohs hardness of 5 or more and an average particle diameter (d ₁ ).
Of particles (A) having a particle size of 0.6 to 3.0 μm in the range of 0.005 to 0.
3% by weight and average particle size (d ₂ ) of 0.06 to 0.8 μ
m of particles (B) containing 0.05 to 3 wt%, and claim 1 or, characterized by satisfying the following formula (3)
The polyester film for high-sensitivity heat-sensitive stencil printing base paper according to 2 . [Equation 2] 2 ≦ d ₁ / d ₂ ≦ 10 (3)