JPH0948181A - Film for high sensitivity thermal stencil printing base sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a film for a high sensitivity thermal stencil printing base sheet having excellent winding characteristics, perforation sensitivity and curl resistance of the film and an excellent resolution and density of an image at the time of printing. SOLUTION: The film for a high sensitivity thermal stencil printing base sheet is a biaxially oriented polyester film having a thickness of 0.5 to 5μm and containing 0.1 to 3.0wt.% of crosslinked polymer organic particles having a particle distribution value (r) of 1.5 or less and a mean particle size of 0.1 to 3.0μm and 0.01 to 1.0wt.% of particles having Moh's hardness of 7 or more and a mean particle size of 0.1 to 0.9μm in polyester (c) having a transesterification rate of 2 to 20% obtained from polyester (a) containing ethylene terephthalate unit of 70mol% or more and polyester (b) containing butylene terephthalate unit of 70mol% or more to satisfy a formula I.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polyester film for heat-sensitive stencil printing base paper. More specifically, the present invention provides a film having excellent winding property, perforation sensitivity and curl resistance of a film by combining and blending specific particles with a specific polyester, and has high resolution with excellent image resolution and density during printing. The present invention relates to a film for 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 required to be excellent in handleability and productivity during film production and base paper production. Specifically, the winding appearance when wound as a roll during film production is also an important element. Air is trapped between the films when wound as a roll. As the film winding speed increases, the amount of air that accompanies the film increases, so that the air layer formed between the films becomes thicker. If this air layer is not quickly reduced during film winding so that the film surface does not come into contact, when air escapes, the film flows to the right or left while riding on the air layer, and the film end surface of the winding roll becomes uneven. Therefore, it is necessary for the film to easily escape air when the film is wound up. Further, it is necessary that problems such as unwinding of the film and running of the film in the process do not occur even when the base paper is prepared.

(2) It is required that the thermal perforation sensitivity is good. That is, it is required to have sufficient heat shrinkage characteristics so that it can be melted with a small amount of heat, and that perforations of an appropriate size can be obtained so that an image at the time of printing becomes clear. (3) It is required that 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, silicone oil, molten dust of the film, and the like do not adhere as dirt on the thermal head, and if they do, the effect of cleaning the dirt on the adhered head is required. (4) It is required to have a strength and elastic modulus that can sufficiently withstand the work at the time of laminating with porous thin paper and printing. In addition, in such work, even if there is a heating step,
Therefore, it is required that problems such as curling of the base paper do not occur.

(5) It is required that the thermal perforation has good gradation. That is, when used as the 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 poor, which is not preferable. It is required to have a thermal perforation property that can clearly distinguish the perforated part and the non-perforated part. 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-62-62).
No. 149496), a film that defines the surface roughness and the number of protrusions (JP-A-63-227634), or a film that defines the heat-shrinking property (JP-A-62-282983, 63-63). -160895
Japanese Patent Laid-Open No. 63-321192, Japanese Patent Laid-Open No. 3-192192
No. 30996 gazette) has been proposed, but it has not been possible to solve all the problems described above.

[0006]

The inventors of the present invention have made extensive studies in view of the above-mentioned problems, and as a result, have found that a biaxially oriented film containing two or more specific particles in a specific polyester mixture is a high-sensitivity heat-sensitive stencil plate. They have found that they are suitable for use as printing base paper, and have completed the present invention.

That is, the gist of the present invention is that the transesterification rate obtained from the polyester (a) containing 70 mol% or more of ethylene terephthalate units and the polyester (b) containing 70 mol% or more of butylene terephthalate units has a transesterification rate of 2 to 10. 20% of polyester (c) has a particle size distribution value (r) of 1.5 or less and an average particle size of 0.1 to 3.0 μm.
0.1 to 3.0% by weight of crosslinked polymer organic particles, and 0.01 to 1.0% by weight of particles having a Mohs hardness of 7 or more and an average particle size of 0.1 to 0.9 μm, A high-sensitivity biaxially oriented polyester film for heat-sensitive stencil printing base paper having a film thickness of 0.5 to 5 μm and satisfying the following formula.

[0008]

[Equation 2]

Hereinafter, the present invention will be described in detail. The difunctional acid component of the polyester in the present invention is mainly an aromatic dicarboxylic acid or its ester-forming derivative, and specifically, terephthalic acid, 2,6-naphthalenedicarboxylic acid, its ester-forming derivative. Examples thereof include dimethyl terephthalate and dimethyl 2,6-naphthalenedicarboxylate. Among these, terephthalic acid and dimethyl terephthalate are preferable. 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 may be a polyester having one kind of aromatic dicarboxylic acid or its ester-forming derivative and one kind of alkylene glycol as a starting material, but it is a copolymer containing two or more kinds of components. Is preferred. As a component to be copolymerized, other than the above, for example, diethylene glycol, neopentyl glycol,
Examples thereof include diol components such as polyalkylene glycol, dicarboxylic acid components such as adipic acid, sebacic acid, phthalic acid and isophthalic acid, trimellitic acid and pyromellitic acid. In addition, homopolymers each composed of a single component, a copolymer containing a homopolymer and two or more components, and a blended polyester of the copolymers are preferable. Among them, polybutylene terephthalate and polyethylene terephthalate or isophthalic acid are preferable. A blended polyester with a polyethylene terephthalate copolymer as a copolymerization component is more preferable.

The melting point of the polyester film of the present invention is
It is usually in the range of 150 to 240 ° C, preferably 160 to 230 ° C. If the melting point is higher than 240 ° C, the high perforation sensitivity aimed at by the present invention may not be obtained, and if it is lower than 150 ° C, the heat-resistant dimensional stability of the film deteriorates, and Curl may occur during storage of the base paper, or the gradation of the printed image may deteriorate. In the present invention, the difference between the highest melting point (Tm2) and the lowest melting point (Tm1) of the film is usually 50 ° C.
Below Tm1 and Tm2, preferably below 30 ° C
May be the same. When the melting point difference is 50 ° C. or higher,
There is a tendency that uniform perforation does not occur in a short time and the gradation of the printed image becomes poor.

The polyester (a) used in the present invention is
Polyester containing terephthalic acid or dimethyl terephthalate and ethylene glycol as main starting materials and containing 70 mol% or more of ethylene terephthalate units. Polyester (b) means butylene terephthalate using terephthalic acid or dimethyl terephthalate and butylene glycol as main starting materials. A polyester containing 70 mol% or more of units.

When the ethylene terephthalate unit and the butylene terephthalate unit are less than 70 mol%, the heat-resistant dimensional stability of the film is deteriorated, curling occurs in the process of manufacturing the base paper or during the storage of the base paper, and the gradation of the printed image. This is not preferable because it deteriorates the property. Moreover, if it exists in the said range, you may each contain the following 3rd components.

The third component is mainly an aromatic dicarboxylic acid or its ester-forming derivative, specifically, terephthalic acid, 2,6-naphthalenedicarboxylic acid, and its ester-forming derivative is terephthalic acid. Examples include dimethyl and dimethyl 2,6-naphthalenedicarboxylate. Examples of the glycol component include ethylene glycol, butylene glycol, propylene glycol, polyethylene glycol, 1.4-cyclohexanedimethanol and the like.

As described above, the object of the present invention is that the film has good winding property and slitting property at the time of manufacturing, does not cause wrinkles or winding deviation during winding, has a good roll appearance, and is a heat-sensitive stencil plate. Heat-resistant dimensional stability when used as a film for printing base paper, and high perforation sensitivity even with a small amount of heat, and thermal perforation sensitivity does not decrease even during multiple plate making, that is, surfactant and silicone oil in the release layer. In addition, it has the effect that the molten debris of the film does not adhere as dirt on the thermal head, and when it adheres, it has the effect of cleaning the dirt on the thermal head that has adhered and at the same time minimizing the abrasion of the thermal head. Another object of the present invention is to provide a base film for heat-sensitive stencil printing base paper which is also advantageous from the standpoint of production.

One of the features of the present invention is a copolymer of the polyester (a) and the polyester (b) obtained by melt-kneading the polyester (a) and the polyester (b). The starting material is a polyester (c) containing 2 to 20% of the amount of the copolymer as the transesterification rate. The transesterification rate as referred to in the present invention is determined by ¹³ C-NMR to be 4
Quaternary carbon can be quantified, and the quaternary carbon peak of terephthalic acid can be obtained by using the fact that the peaks of quaternary carbon are separated into four by the effect of both sides.

When the transesterification rate is less than 2%, a film is not melted with a small amount of heat energy, and perforations having a sufficient size cannot be obtained, which is not preferable. If the transesterification rate exceeds 20%, the heat-resistant dimensional stability when formed into a film deteriorates, curling occurs during the process of manufacturing the base paper or during storage of the base paper, and the gradation of the printed image deteriorates. This is not preferable. Transesterification rate is 2 to 20
As a specific method for obtaining 100% of the polyester (c), there is a method of melt-kneading the polyester (a) and the polyester (b) using an extruder.

Although a known extruder can be used in the present invention, a vented extruder is effective for omitting the polyester drying step, and in order to promote randomization and increase the transesterification rate. Is 2 more than a single axis
The axial extruder is more effective. The transesterification rate of the polyester (c) is greatly affected by the extrusion temperature of the extruder, and when the extrusion temperature is increased, randomization is promoted, and the transesterification rate tends to increase. In any case, the extruder is not limited as long as it satisfies the gist of the present invention.

Further, according to the present invention, there is also a method of using scraps such as ears generated at the time of film production, which are generally called recycled products, which are composed of the composition of polyester (a) and polyester (b). This method is recycling of recycled products, and is an economically advantageous method. As long as it satisfies the gist of the present invention, there is no problem even if a recycled product is blended, and it is an effective method for reducing the manufacturing cost. As a method of obtaining a recycled product, after flaking scraps generated in the polyester film forming step, drying and melting in an extruder to pelletize, and scraps are pelletized as they are using an extruder manufactured by Elema Co. There is a method to make it.

In the present invention, the blending amount of the polyester (a) and the polyester (b) for obtaining the polyester (c) is 30 to 70% by weight of the polyester (a) and 70 to 30% by weight of the polyester (b). Further, the polyester (a) is preferably 40 to 60% by weight, and the polyester (b) is preferably 60 to 40% by weight. If the blending amount of the polyester (a) is less than 30% by weight or the blending amount of the polyester (b) exceeds 70% by weight, the thermal stability tends to be poor, and the heat-resistant dimensional stability of the finally obtained film tends to be poor. There is a possibility that the deterioration may deteriorate, curling may occur during the process of manufacturing the base paper or during the storage of the base paper, or the gradation of the printed image may be deteriorated. Further, the amount of the polyester (a) compounded exceeds 70% by weight, and the amount of the polyester (b) compounded is 3%.
If it is less than 0% by weight, the thermal energy required for perforation becomes high, so that the resolution and printing quality of the finally obtained film during printing may be deteriorated. Another feature of the invention is that the polyester contains two or more particles having different properties. The object of the present application can be achieved by using organic crosslinked particles, particles having a Mohs hardness of 7 or more, and particles having different characteristics. One of the particles is a crosslinked polymer particle and the other particle has a Mohs hardness of 7
The above particles.

The average particle size of the crosslinked polymer particles used in the present invention is 0.1 to 3.0 μm, preferably 0.3 to 2.0 μm.
m, particle size distribution value (r) is 1.5 or less, preferably 1.4
It is the following. If the average particle size is less than 0.1 μm, the film winding properties are poor, and wrinkles may form when the film is wound on a roll, which is not preferable. The average particle size is 3.0 μm
When 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, poor resolution, and poor print quality. It is not preferable because it may be damaged.

Further, the addition amount of the crosslinked polymer particles is 0.1.
It is 3.0% by weight, the number of particles in 1 g of polyester resin is 5.9 × 10 ^{7 to} 1.8 × 10 ¹² , and the addition amount is 0.2 to 2.0% by weight and the number of particles is 1.2 x 10
The range of ^{8 to} 1.2 × 10 ¹² is preferable. When the amount of the crosslinked polymer particles added is less than 0.1% by weight, the film winding property is deteriorated, which is not preferable. On the other hand, if the amount of the crosslinked polymer particles added exceeds 3% by weight, the degree of roughening of the film surface is too large, resulting in uneven heat transfer, uneven perforation, poor resolution, and poor print quality. It is not preferable because it may be damaged. The crosslinked polymer particles used in the present invention include, for example, one or more monovinyl compounds (A) having only one aliphatic unsaturated bond in the molecule and two or more aliphatic vinyl compounds in the molecule as a crosslinking agent. It can be obtained by copolymerizing with one or more compounds (B) having an unsaturated bond by an emulsion polymerization method. The emulsion polymerization method referred to here means emulsion polymerization in a broad sense including concepts such as soap-free emulsion polymerization and seed emulsion polymerization.

As the compound (A) which can be used as a raw material for the crosslinked polymer particles, acrylic acid, methacrylic acid and their alkyl or glycidyl esters,
Maleic anhydride and its alkyl derivatives, vinyl glycidyl ether, vinyl acetate, styrene, alkyl-substituted styrene, etc. can be mentioned. Examples of the compound (B) include divinylbenzene, divinylsulfone, ethylene glycol dimethacrylate, 1,4 butanediol diacrylate and the like. One or more kinds of the compounds (A) and (B) are used, but a compound having a nitrogen atom or ethylene may be copolymerized.

As the polymerization initiator, hydrogen peroxide, potassium persulfate, potassium persulfate-sodium thiosulfate and the like can be used. Further, as the dispersion aid during the polymerization of the crosslinked polymer particles, a fatty acid salt, an alkyl sulfate ester salt,
Anionic surfactants such as alkylbenzene sulfonates, alkyl sulfosuccinates, alkyl naphthalene sulfonates, alkyl diphenyl ether disulfonates, alkyl phosphates, polyoxyethylene alkyl or alkylallyl sulfate ester salts, and polyoxyethylene alkyls. Nonionic interface such as ether, polyoxyethylene alkyl allyl ether, polyoxyethylene derivative, polyoxyethylene-oxypropylene block copolymer, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene sorbitol fatty acid ester, glycerin fatty acid ester Both surfactants and cationic surfactants such as alkyl amine salts and quaternary ammonium salts, and alkyl betaines and amine oxides A surfactant. Among them, anionic surfactants typified by alkyldiphenyl ether disulfonate are preferably used.

In any case, it is preferable that these copolymers have a crosslinked structure and are substantially insoluble, infusible and heat resistant even at high temperatures during the production or molding of polyester. Specifically, crosslinked polymer particles having a weight loss rate of 30% by weight or less, further 20% by weight or less after heat treatment at 300 ° C. for 30 minutes under nitrogen gas flow are desirable.
Further, the crosslinked polymer particles may or may not be porous, but porous is preferable because it is more excellent in affinity with polyester. The particles used in combination with the organic crosslinked polymer particles have a Mohs hardness of 7 or more. When the Mohs hardness is less than 7, stains adhere to the thermal head during plate making many times and the perforation sensitivity decreases, which is not preferable.

Although the mechanism by which particles having a high Mohs hardness give good results to the fouling of the thermal head has not been clarified, particles having a hardness equal to or higher than that of the thermal head have a remarkable effect. It is considered that the cleaning effect can be obtained by polishing the head together with the dirt forming particles forming the heat sensitive head, and by adding particles having a Mohs hardness of 7 or more to polyester, the resolution and density of the image at the time of printing can be improved. It is possible to obtain a film for high-sensitivity heat-sensitive stencil printing base paper, which is excellent in heat-sensitive piercing sensitivity and does not deteriorate the heat-piercing sensitivity even when the plate is made many times.

The particles having a Mohs hardness of 7 or more have an average particle diameter of 0.1 to 0.9 μm, preferably 0.2 to 0.6 μm,
The addition amount is 0.01 to 1.0% by weight, preferably 0.05.
Is about 0.6% by weight. If the average particle size is less than 0.1 μm or if the addition amount is less than 0.01% by weight, the effect of cleaning the dirt adhering to the thermal head cannot be obtained, and as a result, thermal perforation is performed after many times of plate making. Sensitivity decreases and high resolution printing becomes impossible. The average particle size is 0.9
If it exceeds 1.0 μm or the amount of particles exceeds 1.0% by weight, the flatness of the film surface is impaired and heat transfer becomes uneven, resulting in uneven perforation, poor resolution, and poor print quality. It is not preferable because it may damage the Further, the thermal head is polished more than necessary and the life of the thermal head is shortened.

Examples of the inert particles having a Mohs hardness of 7 or more used in the present invention include silicon nitride, boron nitride, zirconia and aluminum oxide particles.
It is not limited to these. Among these, aluminum oxide particles are preferable, as a method for producing the particles, for example, a thermal decomposition method, that is, a method of flame hydrolysis using anhydrous aluminum chloride as a raw material, or an ammonium alum thermal decomposition method, that is, aluminum hydroxide as a raw material. Examples thereof include a method of reacting with sulfuric acid to form aluminum sulfate and then reacting with ammonium sulfate to form ammonium alum for firing. The crystal form of aluminum oxide is preferably γ type, θ type or δ type, and more preferably α type.

Further, in the present invention, the ratio of the average particle size of the organic crosslinked polymer particles and the particles having a Mohs hardness of 7 or more needs to satisfy the following formula.

[0030]

(Equation 3)

If the particle size ratio is less than 0.2, particles having a Mohs hardness of 7 or more, which are blended in order to exert a cleaning effect, are buried in the protrusions of the crosslinked polymer organic particles and stains adhered to the thermal head. The effect of cleaning the sheet is not obtained, and as a result, the thermal perforation sensitivity is reduced after many times of plate making, and high resolution printing cannot be performed. Also, the particle size ratio is 2
If it exceeds, the flatness of the film surface is impaired, heat transfer becomes uneven, perforation becomes non-uniform, the resolution is deteriorated, and the printing quality is impaired, which is not preferable. The particle size of particles having a Mohs hardness of 7 or more is 0.9 μm.
When the particle size ratio exceeds 2, just as when
The thermal head is polished more than necessary and the life of the thermal head is shortened.

The film thickness of the present invention is usually 0.5 to 5 μm.
m, preferably 0.8 to 3 μm. If the film thickness is thin, the heat conduction distance is shortened, and the heat energy required for perforation is also reduced, so that the perforation property is improved, and the resolution and print quality during printing are improved.
There is a tendency that printing is unclear and uneven density is likely to occur,
Printing durability may also be reduced. On the other hand, if the thickness exceeds 5 μm, the piercing property tends to deteriorate, and unevenness may occur during printing. The melting point of the polyester film of the present invention is preferably in the range of 150 to 240 ° C, more preferably 160 to 230 ° C. If the melting point is higher than 240 ° C, high perforation sensitivity may not be obtained, and if it is lower than 150 ° C, the heat-resistant dimensional stability of the film deteriorates, and the curl may be curled 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 deteriorate.

Further, in the present invention, the heat shrinkage stress of the film at 100 ° C. is 500 to 1500 g / mm ² , and further 50 at least in one of the longitudinal and transverse directions.
The range of 0 to 1300 g / mm ² is preferable. When the heat shrinkage stress is less than 500 g / mm ² , the force for expanding the holes at the time of perforation tends to be insufficient, and there is a possibility that perforations having a size sufficient to obtain a clear image during printing cannot be obtained. When the heat shrinkage stress exceeds 1500 g / mm ² , uneven thickness, uneven shade or dimensional change may occur.

In addition to these characteristics, in the present invention, the shrinkage percentage of the film after treatment at 100 ° C. for 3 minutes is preferably 20% or more, more preferably 30 to 80%. If it is less than 20%, the perforation sensitivity may be insufficient and the print-like image density may decrease. If it exceeds 80%,
Perforation unevenness tends to occur easily. The method for obtaining the particle-containing polyester used in the present invention is not particularly limited, but for example, a method of adding the above-mentioned two or more kinds of particles to the polymerization step of polyester or a method of melt-kneading before film formation is preferably used. .

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, printing resolution and printing quality, the film surface is The center line average roughness (Ra) is preferably 0.01 to 0.20 μm, and more preferably 0.02 to 0.15 μm. Ra
Is less than 0.01 μm, it may be difficult to wind the film, and there are cases in which wrinkles cannot be formed into a product. Further, when Ra exceeds 0.20 μm, the flatness of the film surface tends to be impaired and heat transfer tends to be uneven, resulting in uneven perforation, resulting in poor resolution or impaired print quality. . The film of the present invention,
Since it is usually an extremely thin film, the tensile modulus in both the longitudinal and width directions of the film is usually 300 kg / mm
^{When it is 2} or more, preferably 350 kg / mm ² or more, handling workability and printing durability are further improved.

[0036]

BEST MODE FOR CARRYING OUT THE INVENTION Next, a method for producing a 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 increase the adhesion between the sheet and the rotary cooling drum. In the present invention, the electrostatic application adhesion method and / or the liquid application adhesion method are preferably employed.

In the electrostatic application contact method, a linear electrode is usually placed on the upper surface side 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 adhesion method is a method of improving the adhesion between the drum and the sheet by uniformly applying the liquid to the entire or a part of the surface of the rotary cooling drum (for example, only the part in contact with both ends of the sheet). It is. In the present invention, both may be used as needed.

In the present invention, the sheet thus obtained is biaxially stretched to form a film. Specifically, the stretching conditions of the unstretched sheet are preferably in the temperature range of 20 to 100 ° C., more preferably 25 to 80 ° C., and are first unidirectionally stretched by a roll or tenter type stretching machine at 3.0 to 7 ° C. Stretching twice, preferably 3.5 to 7 times. Next, preferably 2 in the direction orthogonal to the first stage.
In the temperature range of 0 to 100 ° C., more preferably 25 to 90 ° C., stretching is performed 3.0 to 7 times, preferably 3.5 to 7 times, more preferably 4.0 to 7 times, and biaxially oriented. Get the 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 magnification 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 as the area ratio.
After heat treatment, the heat treatment after stretching is substantially not performed, or even if it is performed, 110 ° C. or less, further 90 ° C. or less, and the heat treatment time is 1 second to 5 minutes, and the film is stretched within 30% or under a fixed length. It is preferable to carry out.

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 added 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.

[0041]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the scope of the invention. The physical property measuring methods used in the present invention are shown below. (1) Transesterification rate HFIP / CDC using JSX GSX-400 type
Dissolve the film in K ₃ = 3/7 mixed solution and measure at 25
¹³ C-NMR was measured at ° C, and the transesterification rate was calculated by the following formula.

[0042]

## EQU00004 ## Transesterification rate (%) = (A / B) × 100 (In the above formula, A is the peak of transesterified chemical shift (133.4 ppm), and B is the chemical shift of PBT (134.1 ppm). Represents the peak of

(2) Average Particle Size Centrifugal sedimentation type particle size distribution measuring device SA- manufactured by Shimadzu Corporation
The particle size was measured using a CP3 type by the sedimentation method based on Stokes' resistance law. The average particle size was determined using a value of 50% of the integrated (volume basis) in the equivalent spherical distribution of the particles obtained by the measurement. The particle size distribution value (r) was calculated from the following equation.

[0044]

## EQU5 ## Particle size distribution value (r) = d ₂₅ / d ₇₅ (In the above formula, d ₂₅ and d ₇₅ are the cumulative volume of the particle group measured from the large particle side, and 25% and 75% of the total volume of each is measured. Particle size (μm) corresponding to

(3) Average vertical and horizontal thermal 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 that was measured, and the thermal shrinkage was calculated by the following formula. did.

[0046]

(Equation 6) Five points were measured in the longitudinal direction and the transverse direction of the film, and an average value was obtained.

(4) Heat shrinkage stress The film is cut into a strip having a width of 10 mm, and one end is loaded.
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 100 ° C,
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)
Was. Measured at 5 points in the film lengthwise and widthwise directions, and averaged
I asked.

(5) Curling at room temperature Using a Japanese paper made of Manila hemp fiber as a support and a vinyl resin dissolved in toluene as an adhesive on a polyester film having a predetermined thickness, a film and Japanese paper are laminated at 50 ° C. Was dried in an air oven for 10 seconds to obtain a heat-sensitive stencil sheet. Cut the obtained base paper into B4 size and place it on a flat table with the film side up. 2
The curl diameter after 24 hours at 5 ° C. was measured.

(6) Curling at 50 ° C. A heat-sensitive stencil sheet was prepared in the same manner as in the room temperature curl measurement, and the obtained stencil sheet was cut into B4 size, and the film surface was placed on a flat table and placed at 50 ° C. -The curl diameter was measured after processing for 1 week in a thermo-hygrostat having a humidity of 90%.

(7) Winding characteristics A film produced at a line speed of about 170 m / min was wound on a paper tube having a diameter of 15 cm, and the state of the winding end face of 6000 m was observed and classified into the following three ranks. ◎… The end faces are all aligned 〇… The end faces are almost aligned and practically usable △… Some of the end faces are irregular ×… The lower part of the end faces is irregular

(8) Melting point Differential calorimeter SSC580DS manufactured by Seiko Instruments Inc.
It was measured using a model C20. The DSC measurement conditions are as follows. That is, 10 mg of the sample film was
Set in the device, raise the temperature at a rate of 10 ° C / min.
The measurement was performed in the range of 00 ° C., and the melting point was measured as the top of the melting endothermic peak.

(9) Practical characteristics of heat-sensitive stencil printing base paper Washi paper was stuck to the film to prepare 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 portion was observed with a microscope from the film side of the perforated base paper, and the following items were evaluated.

(I) Sensitivity ⊚ A predetermined perforation is surely performed and the size of the perforation is sufficient, and is very good. The predetermined perforation is almost certainly performed and the size of the perforation is also sufficient. On rare occasions, there are portions where the prescribed perforations cannot be obtained or portions where the perforations are insufficient. × ... There are many portions where the prescribed perforations cannot be obtained, and the perforations are insufficient in size, which poses 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 ∘: Clear printing is possible with no density unevenness and bleeding at all, and very good.
Good Δ: Slight unevenness in shades and bleeding are recognized and slightly lacking in sharpness × ... Unevenness in shades, or bleeding and blurring are clearly observed The method for producing the raw material polyester used in the examples is shown below.

"Production of Polyester (a) -1" 80 parts by weight of dimethyl terephthalate, 20 parts of dimethyl isophthalate
Starting material is 60 parts by weight of ethylene glycol,
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., the reaction temperature was gradually raised as methanol was distilled off, and the temperature was set to 230 ° C. after 3 hours. After 4 hours, 0.04 part of ethyl acid phosphate and 0.04 part of antimony trioxide were added to the reaction mixture which had undergone the transesterification reaction substantially, and polycondensation reaction was carried out for 4 hours. That is, the temperature
The temperature was gradually raised from ℃ to 280 ℃. On the other hand, the pressure was gradually reduced from the normal pressure to finally set it to 0.3 mmHg. After 4 hours from the start of the reaction, the reaction was stopped and the polymer was discharged under nitrogen pressure. The intrinsic viscosity of the obtained polyester was 0.75.

"Production of Polyester (b) -1" 100 parts by weight of dimethyl terephthalate, 56 parts by weight of 1,4-butanediol, and 0.005 of tetrabutyl titanate.
Part by weight is placed in a reactor, the reaction start temperature is set to 150 ° C.,
With the evaporation of methanol, gradually raise the reaction temperature,
After 3 hours, the temperature was set to 210 ° C. After 4 hours, 0.005 parts by weight of tetrabutyl titanate as a polymerization catalyst was added to the reaction mixture which had been substantially subjected to the transesterification reaction, and a polycondensation reaction was carried out by an ordinary method. That is, the temperature was gradually raised from 210 ° C to 260 ° 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.
It was 90.

"Production of polyester (c) -1" 50 parts by weight of polyester (a) -1 and polyester (b)-
50 parts by weight are uniformly blended to give an average particle size of 0.70.
0.4 parts by weight of spherical organic crosslinked particles having a particle size distribution value (r) of 1.2 μm and 0.2 parts by weight of α-alumina having a Mohs hardness of 9 and an average particle size of 0.35 μm were mixed, and a vent was used 2 Polyester (c) -1 was produced under the conditions of a temperature of 285 ° C. and a residence time of 4 minutes in a screw extruder. The intrinsic viscosity of the obtained polyester (c) -1 was 0.75 and the transesterification rate was 4.5%.

[Production of Polyester (c) -2] In the production of Polyester (b) -1, 80 parts by weight of dimethyl terephthalate, 20 parts by weight of dimethyl isophthalate and 1,4-butane were used instead of 100 parts by weight of dimethyl terephthalate. 1,4-butanediol 2 instead of 56 parts by weight of diol
Ethylene glycol slurry containing 8 parts by weight, 30 parts by weight of ethylene glycol, and 0.4 parts by weight of spherical organic particles having an average particle size of 0.70 μm and a particle size distribution value (r) of 1.2 after the completion of the transesterification reaction. A method similar to the production of polyester (b) -1 except that 5 parts by weight of ethylene glycol slurry containing 0.2 parts by weight of alumina particles having a Mohs' altitude of 9 and an average particle size of 0.35 μm are added. Thus, polyester (c) -2 was obtained. The intrinsic viscosity of the obtained polyester was 0.76 and the transesterification rate was 98.1%.

[Production of Polyester (c) -3] Polyester (c) -1 was extruded into a sheet form at 265 ° C. from an extruder and subjected to electrostatic cooling using a rotary cooling drum whose surface temperature was set to 30 ° C. Utilized to quench and solidify, thickness 13.5
A substantially amorphous sheet of μm was obtained. 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. Scrap and ears generated when a biaxially oriented film with a thickness of 1.5 μm was produced were crushed, and the temperature was 285 ° C. with a vented biaxial extruder.
-A recycled chip (polyester (c) -3 was produced under the condition of a residence time of 4 minutes. The transesterification rate of the polyester was 5.2%.

"Production of Polyester (c) -4" In the production of polyester (c) -1, spherical organic crosslinked particles are spherical organic crosslinked particles having a particle size of 1.2 µm and a particle size distribution value (r) of 1.2. Polyester (c) -4 was obtained in the same manner as in the production of polyester (c) -1 except that the above was changed. The intrinsic viscosity of the obtained polyester was 0.75. Further, polyester (c) -5 to polyester-20 prepared by blending various particles by the same method were produced, and the added particles are shown in Table 1 below.

[0061]

[Table 1]

[0062]

[Table 2]

[0063]

[Table 3]

[0064]

[Table 4]

Example 1 Polyester (c) -1 was extruded in a sheet form from an extruder at 265 ° C. and rapidly cooled and solidified by a static cooling method using a rotary cooling drum whose surface temperature was set to 30 ° C. Thickness 1
A 3.5 μm substantially amorphous sheet was obtained. 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. Applied, thickness 1.5μ
m biaxially oriented film was produced. Then, the obtained film was adhered to a porous thin paper according to a conventional method to prepare a heat-sensitive stencil printing base paper, and transcript printing was performed.

Examples 2 to 4, Comparative Examples 1 to 1
7 In Example 1, a heat-sensitive stencil printing base paper was prepared in the same manner as in the production of Example 1 except that polyester (c) -1 was changed to polyester (c) -4 in Table 2, and mimetic printing was performed. It was In addition, films of Examples 1 to 4 and Comparative Examples 1 to 17 were manufactured by the same method. The compounding ratio of each polyester (c) is shown in Table 3 below.

[0067]

[Table 5]

The physical properties and practical properties of the obtained polyester film and heat-sensitive stencil printing base paper are shown in Table 4 below.
The results are shown in Tables 5 and 6.

[0069]

[Table 6]

[0070]

[Table 7]

[0071]

[Table 8]

[0072]

[Table 9]

[0073]

[Table 10]

[0074]

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

Claims (1)

[Claims] 1. A polyester (c) having a transesterification rate of 2 to 20%, which is obtained from a polyester (a) containing 70 mol% or more of ethylene terephthalate units and a polyester (b) containing 70 mol% or more of butylene terephthalate units. ), A crosslinked polymer organic particle having a particle size distribution value (r) of 1.5 or less and an average particle diameter of 0.1 to 3.0 μm.
% To 3.0% by weight, 0.01 to 1.0% by weight of particles having a Mohs hardness of 7 or more and an average particle size of 0.1 to 0.9 μm, and satisfying the following formula, the film thickness is 0.5
A biaxially oriented polyester film for high-sensitivity heat-sensitive stencil printing base paper having a thickness of up to 5 μm. [Equation 1]