JPH07164777A - Film for heat-sensitive stencil paper - Google Patents

Abstract

PURPOSE:To provide a film for heat-sensitive stencil printing paper wherein sensitivity resolution have greatly been improved and process and printing whose both letter and solid printing are clear become possible. CONSTITUTION:A film for heat-sensitive stencil paper is a biaxially oriented polyester film having a thickness of 0.4-8.0mum, intrinsic viscosity IV of the film is (1) at least 0.62, the melting point is (2) less than 240 deg.C, a heat shrinkage factor in a lateral direction of the film at 140 deg.C/10min. is (3) at least 40% and in relation to the heat shrinkage factor at 70-160 deg.C, (4) the heat shrinkage factor in a longitudinal direction X 0.9 <= the heat shrinkage factor in lateral direction is given.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film for heat-sensitive stencil printing paper, which is perforated by receiving light or heat from a xenon flash lamp, a thermal head, a laser beam or the like. More specifically, it relates to a film for heat-sensitive stencil printing base paper, which has excellent perforation properties and sharpness at the time of printing.

[0002]

2. Description of the Related Art As a heat-sensitive stencil printing base paper, a film obtained by laminating a heat-sensitive stencil printing base paper and a porous support with an adhesive is usually used. Vinylidene copolymer film, polypropylene film and polyethylene terephthalate copolymer film have been used, and thin paper, Tetoron gauze, etc. have been used as the porous support (for example, JP-A-53-49519).

However, these have the following drawbacks. (1) When solid printing is performed, uneven printing is likely to occur. (2) Since the thickness unevenness is large and the flatness is poor, the suitability for lamination with a porous support is poor, and printing unevenness is likely to occur. (3) Light and shade appear on the printed part, and a clear image cannot be obtained. (4) In addition, unevenness in the thickness of characters partially occurs. (5) A black thin character does not appear and gradation is poor. (6) Sensitivity and resolution differ depending on the adhesive used for adhesion to the porous support.

In general, when a plastic film is used as a film for heat-sensitive stencil printing paper, a sticking phenomenon occurs in which the film is partially fused to the thermal head by the heat given by the thermal head. When this phenomenon occurs, not only the film does not run smoothly, but also the thermal head is significantly contaminated and the sharpness at the time of punching is impaired. In addition, there is a problem that fusion with the document occurs when punching with a flash lamp.

[0005]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above-mentioned drawbacks and to obtain a heat-sensitive material which is clear in both character printing and solid printing, has high gradation, has no uneven printing, and is excellent in stick prevention. To provide a stable film for stencil printing base paper.

[0006]

Means for Solving the Problems As a result of intensive studies for solving the above-mentioned drawbacks, the present inventors have found that the intrinsic viscosity, melting point, heat shrinkage in the width direction, heat shrinkage in the longitudinal direction and heat in the width direction of polyester film. The inventors have found that an optimum film for heat-sensitive stencil printing base paper can be obtained by specifying the relationship with the shrinkage ratio, and have completed the present invention.

That is, the film for heat-sensitive stencil printing base paper according to the present invention is a biaxially stretched polyester film having a thickness of 0.4 to 8.0 μm, and (1) the intrinsic viscosity IV of the film is 0.62 or more, 2) melting point less than 240 ° C,
(3) The heat shrinkage in the film width direction at 140 ° C. for 10 minutes is 40% or more, and (4) with respect to the heat shrinkage at 70 to 160 ° C., longitudinal heat shrinkage × 0.9 ≦ width heat shrinkage. It consists of something that is characterized.

In the present invention, the polyester is a polyester having a dibasic acid and glycol as constituents,
Aromatic dibasic acids include terephthalic acid, isophthalic acid, phthalic acid, naphthalene dicarboxylic acid, diphenyl sulfone dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenoxyethane dicarboxylic acid, cyclohexane dicarboxylic acid, diphenyl dicarboxylic acid, diphenyl thioether dicarboxylic acid, diphenyl Examples thereof include ketone dicarboxylic acid, phenylindane dicarboxylic acid, sodium sulfoisophthalic acid and dibromoterephthalic acid. Examples of the alicyclic dibasic acid include cyclohexanedicarboxylic acid, decalin dicarboxylic acid and hexahydroterephthalic acid. Further, as the aliphatic dibasic acid,
Examples thereof include oxalic acid, succinic acid, adipic acid, azelaic acid, sebacic acid and dimer acid. Examples of the glycol include aliphatic glycols such as ethylene glycol, propylene glycol, tetramethylene glycol, hexamethylene glycol, neopentyl glycol and diethylene glycol, and aromatic diols include naphthalene diol and 2,2-bis (4-hydroxydiphenyl). ) Propane, 2,2-bis (4-hydroxyethoxyphenyl) propane, bis (4-hydroxyphenyl) sulfone, hydroquinone, tetrabromobisphenol A, and the like, and alicyclic diols include cyclohexanedimethanol and cyclohexanediol. And so on.

Further, within the range where the polyester is substantially linear, a polyfunctional compound having three or more functional groups such as glycerin, trimethylolpropane, pentaerythritol,
Trimellitic acid, trimesic acid, pyromellitic acid, tricarballylic acid, gallic acid or the like may be copolymerized, or a monofunctional compound such as o-benzoylbenzoic acid or naphthoic acid may be added and reacted. Further, a polyether such as polyethylene glycol or polytetramethylene glycol or an aliphatic polyester represented by polycaprolactone may be copolymerized.

The polyester of the present invention may be composed of at least two different compatible polyesters. In this case, the polyesters may be regarded as "different polyesters" even if the constituent components are different or homopolymers and copolymers. If the copolymerization components are the same and the copolymerization ratio is different, "different polyesters" may be used. May be considered. In any case, these polyesters are required to be compatible with each other, but the term “compatibility” in the present invention means that the unstretched film is transparent when the polyesters are mixed and melt-extruded. The internal haze of the unstretched film is preferably 40% or less, more preferably 20% or less, and further preferably 10% or less in terms of 100 μm thickness. That is, it is desirable that the polyester be dispersed in a diameter of submicron order or less. In order to compatibilize polyester, a method of reducing the difference in the solubility parameter of the polymer, that is, a method of changing the structure of the polymer, a method of adjusting the viscosity of the polymer, a method of increasing the shearing force at the time of melt extrusion or a compatibilizing agent is used. The method of adding as 3 components etc. is mentioned.

When two or more polyesters are used,
At least one of them is preferably polyester A having a low melting point and high crystallinity, and the other is polyester B compatible with it. Polyester A has a low melting point and high crystallinity. Specifically, the melting point Tm ≦ 240 ° C., Δ
It is preferable that Tcg ≦ 60 ° C. Where ΔTcg
Is the difference Tc-T between the glass transition temperature Tg and the cold crystallization peak temperature Tc when the polymer is measured by a differential scanning calorimeter.
It is a value represented by g. Examples of the polyester A include polybutylene terephthalate, polyhexamethylene terephthalate, polybutylene naphthalate and / or copolymers thereof. As polyester B compatible with polyester A having a low melting point and high crystallinity, ΔTcg
It is preferably ≧ 60 ° C. or substantially amorphous. The polyester B having ΔTcg ≧ 60 ° C. is selected from polyethylene terephthalate, polycyclohexanedimethylene terephthalate, polyethylene naphthalate and / or a copolymer thereof from the viewpoints of heat resistance, mechanical strength, film forming property and the like. Polymers of at least one are preferred.

The substantially amorphous polyester means a polymer having a crystal melting energy ΔHu of 5 cal / g or less measured by a differential scanning calorimeter, or a crystal melting point not observed. To make the polymer amorphous,
It is desirable to introduce or copolymerize a flexible structure. Preferred polymers include polyethylene isophthalate, polyethylene terephthalate / isophthalate copolymer (isophthalate copolymerization rate of 20 mol% or more),
Examples thereof include a copolymer of polyethylene terephthalate and cyclohexanedimethanol (copolymerization ratio of cyclohexanedimethanol 20 to 60 mol%).

As the combination of the polyester A and the polyester B, a compatible combination is selected from the above polymers. Among them, the polyester A has hexanediol as a constituent component, and the polyester B has a cyclohexane ring. It is preferable to have. With this combination, the crystallinity can be imparted to the polyester A, the heat resistance can be imparted to the polyester B, and the polyester A and the polyester B are likely to be compatible with each other. Among them, preferred polymers include polyester A, polyhexamethylene terephthalate, polyhexamethylene terephthalate / cyclohexanedimethanol copolymer, polyhexamethylene terephthalate / isophthalate copolymer, and polyester B, polycyclohexanediphthalate. Examples thereof include methylene terephthalate / ethylene glycol copolymer and polycyclohexane dimethylene terephthalate / isophthalate copolymer.

The mixing ratio of polyester A and polyester B may be arbitrary, but A / B is preferably 1/9 to 4/6.
Is. Further, the third component or more polymers may be mixed.

The glass transition temperature Tg of the polyester film as a whole is preferably 0 ° C. or higher, more preferably 30 ° C. or higher, particularly preferably 40 ° C. or higher. If the Tg is less than 0 ° C., the film will be difficult to handle, and the quality of the film will change over time, causing a problem that the laminate with porous thin paper, for example, curls. In particular, the higher the glass transition temperature of the polyester, which is the main component of the polyester to be mixed, is preferable in terms of film forming property or quality of the film.

In the present invention, the thickness range of the biaxially stretched polyester film constituting the heat sensitive stencil film is as follows:
It is set to 0.4 to 8.0 μm. As described above, first, by specifying the total thickness of the film, it becomes easy to obtain the desired characteristics targeted by the present invention.

Then, the film of the present invention is controlled so that the following conditions are simultaneously satisfied. (1) Intrinsic viscosity IV is 0.62 or more, preferably 0.6
5 or more (2) Melting point is less than 240 ° C., preferably less than 220 ° C. (3) Thermal shrinkage in the film width direction at 140 ° C. for 10 minutes is 40% or more (4) With respect to thermal shrinkage in 70 to 160 ° C. Heat shrinkage x 0.9 ≤ heat shrinkage in width direction, preferably heat shrinkage in longitudinal direction ≤ heat shrinkage in width direction

By keeping the intrinsic viscosity IV and the melting point of the film within the appropriate ranges in this way, as will be described later,
Practical printing characteristics such as perforation sensitivity, independent perforation, character printability, and solid printability are improved.

Furthermore, by setting the heat shrinkage ratio in the width direction at a particular temperature within a particular range, and by setting the magnitude relationship between the heat shrinkage ratio in the longitudinal direction and the heat shrinkage ratio in the width direction at a particular temperature to be a particular relationship, In addition to the above printing practical characteristics, processing characteristics and handling characteristics are improved.

The specific intrinsic viscosity and melting point as described above can be adjusted mainly by the characteristics of the raw materials, and the specific heat shrinkage characteristics are obtained by adjusting the heat treatment conditions after biaxial stretching, as shown in the film production method described later. be able to.

In the present invention, when the characteristics of the heat-sensitive film, that is, the center line average roughness, the maximum roughness and the number of projections on the surface are within the ranges described below, the effects of the present invention are more remarkably exhibited, which is preferable.

In the present invention, the center line average roughness (Ra) of the heat-sensitive film is preferably 0.03 to 0.5 μm, more preferably 0.03 to 0.3 μm. If the center line average roughness is less than 0.03 μm, winding and handling will be quite difficult and creases will be formed, resulting in a decrease in productivity. On the other hand, when Ra exceeds 0.5 μm, the surface becomes rough and becomes too opaque, resulting in a significant decrease in sensitivity.

In the present invention, the heat-sensitive film has a maximum roughness (Rt) of preferably 0.3 to 4.0 μm, more preferably 0.3 to 3.5 μm. Maximum roughness 0.3 μm
If it is less than the above range, slipperiness is deteriorated, air bleeding is bad, vertical wrinkles are contained, and windability is deteriorated. On the other hand, if it exceeds 4.0 μm, not only the sensitivity is lowered but also the film is broken to lower the productivity.

In the present invention, the heat-sensitive film is 1 μmφ
The number of surface protrusions is preferably 2,000 to 10,0.
00 / mm ² , more preferably 2,500 to 8,000
The number is 0 / mm ² . Below 2,000 / mm ² ,
The slipperiness and the winding property are deteriorated, and when it exceeds 10,000 pieces / mm ² , the transparency is lowered and the sensitivity and the resolution are lowered.

The number of protrusions of 8 μmφ to 20 μmφ is preferably 10 to 1,000 / mm ² , and more preferably 20 to 800 / mm ² . 10 /
When it is less than mm ² , the slipperiness is deteriorated, and the film meanders at the time of winding to deteriorate the winding property. Also 1,000 /
If it exceeds mm ² , not only the quality is deteriorated but also the film is broken to lower the productivity.

In the present invention, in order to control the surface morphology of the heat-sensitive film, that is, the surface roughness, the number of protrusions, and the diameter of the protrusions in the above-mentioned preferable ranges, inert particles are used as the thermoplastic resin to be extruded in the production method described later. It is desirable to make a master polymer containing the above and blend with the main polymer. In this case, the master polymer has a melting point of 0 to 100 ° C., preferably 20 to 80, more than that of the main component polymer.
It is preferable that the temperature is higher by 0 ° C. and / or the intrinsic viscosity is higher by 0.2 to 1.0. Further, the main component polymer and the master polymer are preferably compatible with each other to some extent or more. Furthermore, it goes without saying that the specific surface morphology can be controlled to some extent by the shear stress at the time of extrusion, the basis weight of the filter, the extrusion conditions and the like.

The inert particles used in the present invention include:
Particles selected from oxides or inorganic salts of elements of Group IIA, IIIB, IVA, IVB of the element period, such as calcium carbonate obtained as a synthetic or natural product, wet silica (silicon dioxide), dry silica (silicon dioxide), Examples thereof include aluminum silicate (kaolinite), barium sulfate, calcium phosphate, talc, titanium dioxide, aluminum oxide, aluminum hydroxide and calcium silicate.

The average particle diameter of the above-mentioned inert particles is from 0.1 to 0.1
It is preferably 3 μm. Further, the master chip concentration of the inert particles is preferably 0.5 to 10% by weight, more preferably 1.0 to 7.0% by weight in order to form a specific surface morphology. The concentration of inert particles in the heat-sensitive film varies depending on the type of particles, particle size, etc., but is 0.05 to 2.0% by weight, preferably 0.1 to 1.
0% by weight is preferred for obtaining a specific surface morphology.

In the present invention, the heat-sensitive film may be added with an additive having an absorption peak in the wavelength range of flash light irradiation. In addition, additives such as an antioxidant, a heat stabilizer, a lubricant, an antistatic agent, a dye and a pigment may be added if necessary.

The film may have a structure of two or more layers, and inert particles or other additives may be added to either layer. At that time, each layer may be coextruded or may be formed into a film by an extrusion laminating method or a coating method.

Next, the method for producing the polyester film of the present invention will be described, but the present invention is not limited to such an example. The dried polymer chips are fed to an extruder and heated to a temperature above the melting point of the polymer to melt it. Then
The melted polymer is extruded from a slit-shaped T die and adhered to a cooling roll to be solidified to obtain a cast film. In order to improve the adhesion between the molten sheet and the cooling roll, the electrostatic application adhesion method and / or the liquid surface coating adhesion method are usually preferably used. The film is further biaxially stretched. Preferably, the glass transition temperature of the polymer or higher, for example 40 to
It is stretched 2.3 to 7 times in the longitudinal direction with a group of rolls heated to 100 ° C., and then 3 times in the transverse direction, preferably at 45 to 110 ° C.
~ 7 times stretch. A method in which unidirectional stretching is performed in two or more steps can be used, but in that case also, the final stretching ratio is preferably within the above range. In the case of the present invention, it is preferable that the stretching temperature in the transverse direction is lower than that in the longitudinal direction and the stretching ratio is higher than that in the longitudinal direction. It is also possible to simultaneously biaxially stretch the cast film so that the area ratio becomes 6 to 30 times.

The thus-obtained film is heat-treated, and if necessary, before and / or after the heat-treatment, the film is vertically and / or re-oriented.
Alternatively, it may be stretched in the transverse direction. Heat treatment temperature is 90-1
The temperature is 80 ° C., preferably 90 to 150 ° C., and the heat treatment time is usually 1 second to 5 minutes. The heat shrinkage ratio of the present invention can be adjusted under these heat treatment conditions. Further, the cooling rate of the film after the heat treatment also affects the heat shrinkage property. For example, after the heat treatment, the film can be rapidly or slowly cooled, or an intermediate cooling zone can be provided to adjust the heat shrinkage rate. Further, in the case of the present invention, it may be relaxed in the range of 0 to 5% in the longitudinal direction during heat treatment or cooling.

The film may be coated if necessary. In the case of the present invention, a release layer may be provided on the film to impart sticking-preventing property and anti-adhesion property to the original, or adhesiveness to the porous support and antistatic property. The coating solution used is one dissolved in water, emulsified or suspended in view of explosion proof and environmental pollution.
The coating layer has a method of applying to a biaxially stretched film after completion of crystal orientation or a method of applying to a film before completion of crystal orientation and then stretching, but the latter method is required in order to more significantly exhibit the effect of the present invention. Is particularly preferable. The coating method is not particularly limited, but it is preferable to use a roll coater, a gravure coater, a reverse coater, a kiss coater, a bar coater or the like. Before application, the application surface may be subjected to corona discharge treatment in air or other various atmospheres, if necessary. Further, the coating layer in the present invention, if necessary, a defoaming agent, a coating cross-linking agent,
A thickener, an organic lubricant, inorganic particles, an antioxidant, an ultraviolet absorber, a foaming agent, a dye, a pigment and the like may be contained.

If necessary, inorganic particles may be added to the coating layer. Typical examples thereof are preferably 1 μm or less in average particle diameter, more preferably 0.5 μm or less in average particle diameter, and particularly preferably. Those having a particle size of 0.2 μm or less, and specifically include kaolin, silica, silica sol, calcium carbonate, titanium oxide, barium salt, alumina, molybdenum sulfide, carbon black, zirconium, etc., but are not limited to these. Absent.

Further, the film of the present invention may be peeled off from a laminated film with another thermoplastic polymer (II) having excellent peelability to obtain a biaxially stretched thermoplastic film. By doing so, a thin film can be stably formed. The polymer (II) is any polymer selected from polyolefin, polyphenylene sulfide, fluorine-based polymer and the like.

The layer (II) has a peeling force of 10 g / cm or less when peeled off from the film (I) of the present invention, preferably 0.
1-2 g / cm, more preferably 0.2-0.8 g /
The effect of the present invention is remarkable in the range of cm. If the peeling force is too small, peeling between film layers occurs during stretching or film transportation, uniform stretching cannot be performed, the film is wrapped around a stretching roll, or the film peels off during film transportation, such as wrinkles or tears. Trouble may occur. On the other hand, if the peeling force is too large, the film cannot be peeled at a high speed and the film may be torn or pinholes may be formed. Therefore, in order to maintain the peeling force within the above range, the polymer, especially the (II) layer, contains 0.001 to 1% by weight, preferably 0.005 to 0.5% by weight of a non-particulate lubricant. It is good to have been.

A non-particulate lubricant is a liquid having a melting point or a softening temperature of 200.degree.
The following substances may be used as long as they impart film lubricity, and specific examples are as follows. When two or more kinds of these substances are contained in the film, the total amount thereof should be within the above content range.

Specific examples of the non-particulate lubricant include (1) aliphatic hydrocarbon liquid paraffin, microcrystalline wax, natural paraffin, synthetic paraffin, polyethylene wax,
Polypropylene wax etc. (2) Higher fatty acid or metal salt thereof Stearic acid, calcium stearate, hydroxystearic acid, hardened oil, sodium montanate, etc. (3) Aliphatic amides Stearic acid amide, oleic acid amide, erucic acid amide, ricinoleic acid amide, behenamide, methylenebisstearamide and the like. (4) Fatty acid ester n-butyl stearate, methyl hydroxy stearate, myricyl serotinate, polyhydric alcohol fatty acid ester, ester wax and the like. (5) Fatty acid ketone, ketone wax, etc. (6) Fatty acid alcohol Lauryl alcohol, stearyl alcohol, myristyl alcohol, cetyl alcohol and the like. (7) Partial ester of fatty acid and polyhydric alcohol Glycerin fatty acid ester, hydroxystearic acid triglyceride, sorbitan fatty acid ester and the like. (8) Nonionic surfactant Polyoxyethylene alkyl ether, polyoxyethylene phenyl ether, polyoxyethylene alkylamide, polyoxyethylene fatty acid ester and the like. (9) Silicon oil Linear methyl silicone oil, methylphenyl silicone oil, modified silicone oil, etc. (10) Fluorine-based surfactant Fluoroalkylcarboxylic acid, perfluoroalkylcarboxylic acid, monoperfluoroalkylethyl phosphate, perfluoroalkyl sulfonate, etc.

Inorganic fine particles having an average particle size of 0.001 to 1 μm, for example, dry silica, wet silica, zeolite, calcium carbonate, calcium phosphate, kaolin, kaolinite, clay, talc can be used in combination with the above-mentioned non-particulate lubricant. , Titanium oxide, alumina, zirconia, aluminum hydroxide, etc. in the (I) layer and / or (II) layer.
In many cases, the effect of the non-particulate lubricant can be enhanced synergistically if the content of 01 to 0.5% by weight is contained.

The polyester film of the present invention thus obtained can be made into a heat-sensitive stencil printing base paper by laminating a predetermined porous thin paper with a known adhesive according to a conventional method.

[Measurement Method of Physical Properties and Evaluation Method of Effect] The characteristic values of the present invention are based on the following measurement methods and evaluation criteria. (1) Glass transition temperature, cold crystallization peak temperature, melting point 10 mg of polyester was set in a PERKIN ELMER differential scanning calorimeter (DSC-2 type) and heated at a rate of 20 ° C./min under a nitrogen stream. Then, the average value of the temperature at which the baseline starts to be biased and the temperature at which the baseline returns to the new baseline is taken as the glass transition temperature. Further, the peak of the exothermic peak due to crystallization was the cold crystallization peak temperature, and the peak of the crystal melting endothermic peak was the melting point.

(2) Heat Shrinkage A film sample of 100 mm square is set at a predetermined temperature (120
After immersing in silicone oil set to ℃) for 1 minute,
The shrinkage amount of the film was obtained and the ratio to the original size was expressed as a percentage.

(3) Practical characteristics of heat-sensitive stencil printing Washi paper of a film was stuck 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 made at 9 mJ and 0112 mJ. The perforated state of the gradation image portion was observed with a microscope from the film side of the plate-making base paper, and the following items were evaluated.

(I) Perforation sensitivity ◯: The predetermined perforation is surely performed and is good. (Triangle | delta): There is a part which cannot obtain a predetermined perforation, but there is no problem in practical use. ×: There are many places where the predetermined perforation cannot be obtained,
There is a problem in practical use.

(Ii) Independent perforation ◯: Each dot is independently perforated. Δ: Perforations are formed almost independently, and there is no practical problem. ×: Dots adjacent to each other are connected, which is a practical problem.

Further, the stencil sheet was used for printing with a lithograph AP7200 printer manufactured by Riso Kagaku Kogyo Co., Ltd., and the following characteristics of the obtained characters and images were visually judged.

(Iii) Character printability In terms of presence / absence of missing characters, presence / absence of uneven thickness of characters is clearly marked as unusable, and marked with ○ is completely unproblematic. Although there is unevenness, usable ones are indicated by Δ.

(Iv) Evaluation of solid printability: (circle filled with black inside) 0.5, 1.
Using the base papers of 0, 3.0, 10.0 and 30.0 mmφ, the plate-made and printed ones were evaluated as follows. Correspondence with the base paper size of solid printing In the evaluation of uneven density of solid printing, those that are obviously unusable are marked with x.
Those with no problem are shown with a circle, and those with a problem but usable are shown with a triangle.

(4) Number of surface protrusions Al was vapor-deposited on the sample film to a thickness of about 100 nm to obtain an observation sample. This sample was magnified using a Leitz optical microscope (reflection method) and a Hi-vision compatible image analysis device Pierce IV manufactured by Pierce Co., Ltd., and projections were made by using an image with contrast on the projections (monitor magnifying power: 373 times). The size and number of Here, the size of the protrusion is represented by a diameter (circle equivalent diameter) when the area occupied by the protrusion is converted into a circle.

(5) Center Line Average Roughness (Ra), Maximum Roughness (Rt) It was measured using a stylus type surface roughness meter according to JIS-B-0601. In addition, using a high precision thin film step measuring instrument (model: ET-10) manufactured by Kosaka Laboratory Ltd., stylus diameter cone type 0.5 μR, load 5 mg, cutoff 0.08.
mm.

(6) Intrinsic viscosity Measured at 25 ° C. using an o-chlorophenol solvent.

(7) Compatibility The internal haze of an unstretched sheet obtained by extruding mixed variables was measured. Film haze is ASTM-D1
It was measured according to 003-52.

(8) Average particle size of particles Centrifugal sedimentation type particle size distribution analyzer SA manufactured by Shimadzu Corporation
-The size of particles was measured by a sedimentation method based on Stokes's law using CP3 type. The average particle diameter (d50) was obtained by using the value of 50% (according to weight) in the equivalent spherical distribution of the particles obtained by the measurement.

[0054]

EXAMPLES The present invention will be specifically described below based on examples. Example 1 Dimethyl terephthalate / dimethyl isophthalate (molar ratio: 75/25) was used as the dicarboxylic acid component, and ethylene glycol was used as the glycol component. Polymerization was carried out by a conventional method, and silica particles having an average particle size of 1.5 μm were added to the mixture. 0.4 wt% was added to obtain a polymer having an intrinsic viscosity of 0.73. This polymer was extruded in a sheet form at 270 ° C. from a vent type twin-screw extruder, and cooled and solidified on a rotating cooling drum set at 25 ° C. by using an electrostatic application method. Next, the film is vertically oriented at 92 ° C., 3.4 times, and transversely at 90 ° C., 5.0 times.
The film was double-stretched and further heat-treated at 100 ° C. for 5 seconds to produce a biaxially stretched polyester film having a thickness of 1.5 μm.

Comparative Example 1 Using the same polymer as in Example 1, the film was stretched in the machine direction at 92 ° C. and 3.6 times, and in the transverse direction at 95 ° C. and 3.6 times, and further at 100 ° C. for 5 seconds. Heat treated, thickness 1.7μ
m biaxially oriented polyester film was produced.

Example 2 As a polyester, the dicarboxylic acid component was dimethyl terephthalate and the glycol component was ethylene glycol / diethylene glycol (molar ratio: 70/30) and polymerized by a conventional method to obtain a polymer having an intrinsic viscosity of 0.75. It was The film is 70 ℃ in the vertical direction, 3.3 times, 75 ℃ in the horizontal direction,
The film was stretched 4.2 times and further heat-treated at 100 ° C. for 5 seconds to produce a biaxially stretched polyester film having a thickness of 1.7 μm.

Example 3 As polyester A, the dicarboxylic acid component was dimethyl terephthalate / dimethyl isophthalate (molar ratio: 83/1
7), ethylene glycol as a glycol component is polymerized by a conventional method, and then solid-phase polymerization is performed to make the specific year 0.
90 polymers were obtained. As polyester B, dimethyl terephthalate / dimethyl isophthalate (molar ratio: 75/25) was used as the dicarboxylic acid component, and ethylene glycol was used as the glycol component, with an average particle size of 1.5 μm.
0.7% by weight of silica particles was added and polymerized by a conventional method to prepare a polymer having an intrinsic viscosity of 0.65. Polyesters A and B were blended in a ratio of 30:70, and the film was stretched 90 ° C and 3.6 times in the longitudinal direction and 95 ° C and 5.0 times in the transverse direction, and further heat-treated at 120 ° C for 5 seconds to give a thickness. A 1.5 μm biaxially oriented polyester film was produced.

The thus obtained film was laminated on a porous thin paper according to a conventional method to prepare a heat-sensitive stencil sheet, which was applied to a plate making and printing machine, and its properties were evaluated. As shown in Table 1, excellent printing practical properties can be obtained by adjusting the intrinsic viscosity, melting point, and heat shrinkage rate specified in the present invention.

[0059]

[Table 1]

[0060]

The following excellent effects can be obtained by the film for heat-sensitive stencil printing base paper of the present invention. (1) Vivid plate making and printing are possible for both characters and solid printing. (2) With letter and solid printing, it is possible to perform plate making and printing without unevenness in thickness and unevenness in light and shade. (3) The sensitivity and resolution are significantly improved.

Claims (1)

[Claims] 1. A biaxially stretched polyester film having a thickness of 0.4 to 8.0 μm, wherein (1) the intrinsic viscosity IV of the film is 0.62 or more, (2) the melting point is less than 240 ° C., and (3) The heat shrinkage in the film width direction at 140 ° C. for 10 minutes is 40% or more, and (4) the heat shrinkage in 70 to 160 ° C. is longitudinal heat shrinkage × 0.9 ≦ width heat shrinkage. Characteristic heat sensitive stencil base film.