JPH0768965A - Polyester film for high-sensitivity thermal stencil printing base paper - Google Patents

Abstract

PURPOSE:To provide such a polyester film for high-sensitivity thermal stencil printing base paper that resistance to curling, perforation sensitivity, resolution of an image in a time for printing and resistance to printing are excellent. CONSTITUTION:Composite crosslinking high molecular particles are obtained by treating the surfaces of crosslinking high polymer particles having 0.3-3mum average particle diameter and >=0.5 particle size distribution value (Y) by fine particles which have >=7 Mohs hardness, 5-100munm average primary particle diameter and <=0.2mum average secondary particle diameter. A polyester film is blended with the composite crosslinking polymer particles at 0.1-2wt.%. A polyester film for high-sensitivity thermal stencil printing base paper has 150-240 deg.C melting point and 0.5-3mum thickness.

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, it relates to a film for high-sensitivity heat-sensitive stencil printing base paper which is excellent in curl resistance, perforation sensitivity, image resolution during printing and printing durability.

[0002]

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

(3) The thermal perforation sensitivity is good. That is,
It must have sufficient heat-shrinkability so that it can be melted with a small amount of heat and that perforations of an appropriate size can be obtained so that the image during printing becomes clear. (4) The gradation of thermal perforation is good. When used as a base paper, if the portion other than the portion to be perforated is melted due to the influence of the perforations in the periphery, the gradation of the printed image becomes inferior, which is not preferable. In other words, it is necessary to have a thermal perforation property that allows the part to be perforated and the part not to be perforated to be clearly distinguished.

(5) The thermal perforation sensitivity does not decrease even when the plate is made many times. That is, it is necessary that the surface-active agent of the release layer, the silicone oil, the molten dust of the film, and the like do not adhere as dirt on the thermal head. Conventionally, a biaxially stretched film intended for a thermoplastic resin as a film used for such an application, the film having improved printing characteristics by defining its thermal characteristics (JP-A-62-149496), surface Of which the roughness and the number of protrusions are specified (Japanese Patent Laid-Open No. 63-227634).
Or Japanese Patent Laid-Open No. 63-1608.
No. 95, Japanese Patent Laid-Open No. 63-321192, Japanese Patent Laid-Open No. 3-30996) and the like have been proposed, but all of the above problems cannot be solved.

[0005]

Means for Solving the Problems As a result of intensive studies made by the present inventors in view of the above problems, a biaxially oriented film made of a specific polyester containing specific particles is suitable for use as a base paper for heat-sensitive stencil printing. As a result, they have completed the present invention. That is, the gist of the present invention is that the surface of crosslinked polymer particles having an average particle size of 0.3 to 3 μm and a particle size distribution value (r) of 1.5 or less has a Mohs hardness of 7 or more and an average primary particle size of 5 to 5. The composite crosslinked polymer particles obtained by treating with fine particles having a particle size of 100 nm and an average secondary particle size of 0.2 μm or less are 0.1.
It is a polyester film containing 1 to 2% by weight and has a melting point of 150 to 240 ° C. and a thickness of 0.5 to 3 μm, which is a polyester film for high-sensitivity heat-sensitive stencil printing base paper.

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

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

The melting point of the polyester film of the present invention is
It is in the range of 150 to 240 ° C, preferably 160 to 230 ° C. When the melting point is higher than 240 ° C, the high perforation sensitivity that is the object of the present invention cannot be obtained, and when the melting point is lower than 150 ° C, the heat-resistant dimensional stability of the film is deteriorated, and the process for producing the base paper and the preservation of the base paper are suppressed. It is not preferable because curling occurs inside and the gradation of the printed image deteriorates. In the present invention, the difference between the highest melting point (Tm ₂ ) and the lowest melting point (Tm ₁ ) is usually less than 50 ° C.
m ₁ and Tm ₂ may be the same. This temperature difference is 5
At 0 ° C or higher, uniform perforation may not occur in a short time.

The film thickness of the present invention is 0.5 to 3 μm,
Preferably 0.5 to 2 μm, more preferably 0.5 to
It is 1.5 μm. When the film thickness is thin, the heat conduction distance is shortened, and the heat energy required at the time of perforation is also reduced, so that the perforability is improved, and the resolution and print quality during printing are improved, but when the film thickness is less than 0.5 μm Printing is unclear, uneven density is likely to occur, and printing durability is significantly deteriorated, which is not preferable. Also, the film thickness is 3
If it exceeds μm, the perforation property is deteriorated and unevenness occurs during printing.

The film of the present invention is used in order 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. To prevent this, the film is usually provided with appropriate slipperiness. For that purpose, it is preferable to adopt a method of forming fine protrusions on the surface by fine inert particles, unevenness in heat transfer occurs if the size and number of protrusions are inappropriate, and perforation becomes non-uniform, The resolution may be poor or the print quality may be impaired.

An important constituent feature of the present invention is to use composite crosslinked polymer particles surface-treated with fine particles of high hardness having a Mohs' hardness of 7 or more as particles to be incorporated in polyester. The fine cross-linked polymer particles used in the present invention have an average particle size of 0.3 to 3.0 μm and a particle size distribution value (r) of 1.5 or less, preferably an average particle size of 0.3 to 3.0.
It has a particle size distribution value (r) of 2.0 μm and 1.3 or less. If the average particle size of the crosslinked polymer particles used is less than 0.3 μm, the winding properties will be poor, which is not preferable. In addition, the average particle size exceeds 3.0 μm, and the particle size distribution value (r) is 1.5.
If it exceeds, the flatness of the film surface is impaired, heat transfer becomes uneven, perforation becomes uneven, the resolution is deteriorated, and the printing quality is impaired, which is not preferable.

The crosslinked polymer particles applicable to the present invention include, for example, one or more monovinyl compounds (A) having only one aliphatic unsaturated bond in the molecule and 2 in the molecule as a crosslinking agent. Examples thereof include crosslinked polymer particles obtained by copolymerizing one or more compounds (B) having at least one aliphatic unsaturated bond by an emulsion polymerization method.
The emulsion polymerization method as used herein refers to emulsion polymerization in a broad sense including concepts such as soap-free emulsion polymerization and seed emulsion polymerization.

Examples of the compound (A) include acrylic acid, methacrylic acid and their alkyl or glycidyl esters, maleic anhydride and its alkyl derivatives, vinyl glycidyl ether, vinyl acetate, styrene and alkyl-substituted styrene. it can. Further, as the above compound (B), divinylbenzene, divinyl sulfone, ethylene glycol dimethacrylate,
1,4 butanediol diacrylate etc. can be mentioned. 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 for the emulsion polymerization, hydrogen peroxide, potassium persulfate, potassium persulfate-sodium thiosulfate and the like can be used. As a dispersion aid during particle polymerization, a fatty acid salt, an alkyl sulfate ester salt, an alkylbenzene sulfonate, an alkylsulfosuccinate, an alkylnaphthalene sulfonate, an alkyl diphenyl ether disulphonate, an alkyl phosphate, a polyoxyethylene alkyl or Anionic surfactant such as alkylallyl sulfate ester salt, polyoxyethylene alkyl ether, polyoxyethylene alkyl allyl ether, polyoxyethylene derivative, polyoxyethylene-oxypropylene block copolymer, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid Nonionic surfactants such as esters, polyoxyethylene sorbitol fatty acid esters, glycerin fatty acid esters, alkylamine salts, quaternary ammonium salts Cationic surfactants and alkyl betaines, amphoteric surfactants such as amine oxides. Among them, anionic surfactants typified by alkyldiphenyl ether disulphonic acid salts are particularly preferably used.

In any case, it is desirable 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, under nitrogen gas flow 30
The weight loss rate after heat treatment at 0 ° C for 30 minutes is usually 30.
Crosslinked polymer particles are used in an amount of not more than 20% by weight, preferably not more than 20% by weight.

The crosslinked polymer particles may or may not be porous, but the former is preferred because it has a better affinity with polyester. The greatest feature of the present invention is that composite crosslinked polymer particles surface-treated with fine particles having a Mohs hardness of 7 or more are used. With the crosslinked polymer particles alone, the particles often aggregate, especially when the functional group density of the particles is low or when the amount of the polyester compounded is large. This is particularly remarkable when the stirring strength during polyester polymerization is weak.

However, if the composite crosslinked polymer particles surface-treated with specific fine particles are used, not only the dispersibility in the polyester can be remarkably improved, but also the polyester film containing the particles is used. The base paper for heat-sensitive stencil printing exhibits a cleaning effect of the surface-active agent of the release layer and silicon oil that adheres as stains on the heat-sensitive head, and the molten residue of the film, when the plate is made many times, and as a result, the thermal perforation sensitivity decreases. The unexpected effect of not doing so is enjoyed.

Examples of the inert particles having a Mohs hardness of 7 or more used in the present invention include silicon nitride, boron nitride, celite,
Examples thereof include zirconia and aluminum oxide particles, but are not limited to these. Among these, aluminum oxide particles are preferable, and 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 is used. 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 obtained by these methods is preferably γ type, θ type or δ type, and more preferably δ type. The average primary particle size of fine particles having a Mohs hardness of 7 or more used in the present invention is 5 to 100 nm, preferably 10 to 50 nm, but often 0.5 μm.
Since aggregates exceeding 5 are formed, it is desirable to appropriately crush and use. When the average primary particle size is less than 5 nm, a strong aggregate is formed, which is preferable.
If it exceeds, the effect of improving dispersion in polyester becomes insufficient, which is not preferable.

The average secondary particle diameter of the agglomerates of fine particles having a Mohs hardness of 7 or more coated on the crosslinked polymer particles of the present invention is 0.2.
μm or less and smaller than the average particle size of the crosslinked polymer particles to be coated, specifically, ½ or less, and further 1 /
It is preferably 5 or less, particularly preferably 1/10 or less, and the average secondary particle diameter is preferably 0.03 to 0.1 μm. If the average secondary particle size of the secondary agglomerates of fine particles having a Mohs hardness of 7 or more exceeds 0.2 μm, the effect of improving the dispersibility during polyester polymerization becomes insufficient. The amount thereof is usually 0.1 to 2 times, preferably 0.3 to 1 times the weight of the crosslinked polymer particles. This value is 0.1
If the amount is less than double the dispersibility may not be improved, and even if this value exceeds the double amount, the dispersibility is no longer improved any more, and the abrasion of the slit blade during film slitting is remarkable due to the particles. Is not preferable.

As a method for coating the surface of the crosslinked polymer particles with fine particles having a Mohs hardness of 7 or more, for example, when the zeta potential value of the crosslinked polymer particles dispersed in an aqueous solution is negatively (-) charged. Is added to the aqueous solution of fine particles having a positive zeta potential value (+) of Mohs hardness of 7 or more, and the mixture is treated for 3 to 5 hours with stirring to obtain fine particles of Mohs hardness of 7 or more on the surface of the crosslinked polymer particles. The particles can be coated, but are not limited to this method.

In the present invention, the amount of the composite crosslinked polymer particles surface-treated with fine particles having a Mohs hardness of 7 or more in the polyester is 0.1 to 2% by weight, preferably 0.05 to 2% by weight. . If the blending amount is less than 0.1% by weight, the winding property of the film is inferior, which is not preferable. On the other hand, if it exceeds 2% by weight, the degree of surface roughening of the film is too large, heat transfer becomes uneven, perforation becomes uneven, the resolution is deteriorated, and the printing quality is impaired, which is not preferable.

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 0.02 to 0.20 μm, and more preferably 0.05 to 0.15 μm. Ra is 0.
If it is less than 02 μm, the winding characteristics may be inferior.
If the thickness exceeds μm, the degree of roughening of the film surface tends to be too large, uneven heat transfer may occur, uneven perforation may occur, resolution may be deteriorated, and print quality may be impaired. The film of the present invention usually has a heat shrinkage stress (F) of 100 to 10 after treated at 80 ° C. for 10 seconds.
800 g / mm ² , preferably 200-700 g / mm
^{Is 2} . If the shrinkage stress F is less than 100 g / mm ² , the force for expanding the holes during punching may be insufficient, and it may not be possible to obtain perforations having a size sufficient to obtain a clear image during printing. If the shrinkage stress F exceeds 800 g / mm ² , uneven thickness, uneven shade or dimensional change may occur.

The heat shrinkage (S) after the treatment at 80 ° C. for 10 minutes is preferably 5 to 50%, more preferably 10 to 40%. If the shrinkage ratio S is less than 5%, the perforation sensitivity may be insufficient and the image density during printing may be reduced. If the shrinkage ratio S exceeds 50%, unevenness in perforation tends to occur. Since the film of the present invention is an extremely thin film, the tensile elastic modulus in both the longitudinal direction and the width direction of the film is usually 300 kg / mm ² or more, preferably 350 k / mm ^2.
When it is g / mm ² or more, handling workability and printing durability are further improved. Next, a method for producing the polyester film of the present invention will be described.

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

The sheet thus obtained is stretched biaxially to form a film. Describing the stretching conditions specifically, the unstretched sheet is preferably 20 to 100.
In the temperature range of 0.degree. C., more preferably 25 to 80.degree. C., the film is first drawn in one direction by a roll or tenter type drawing machine at 2.5 to 7 times, preferably at 3.0 to 5 times. Next, preferably 20 to 100 ° C. in a direction orthogonal to the first step,
More preferably 2.5 to 7 in the temperature range of 25 to 90 ° C.
The film is stretched twice, preferably 3.0 to 5 times to obtain a biaxially oriented film.

A method in which unidirectional stretching is performed in two or more steps 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 6 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 6 times or more as an area ratio, the heat treatment after stretching is not substantially performed, or 110 ° C. or less even if performed, It is preferable that the temperature is 90 ° C. or lower, the heat treatment time is 1 second to 5 minutes, and the film is stretched within 30% or under a fixed length.

In addition, when a predetermined porous thin paper is laminated with a known adhesive according to a conventional method to produce a heat-sensitive stencil printing base paper, a film is dried during a drying step at about 40 to 50 ° C. and during long-term storage in the summer. Curl may occur due to the contraction of the. Therefore, in the present invention, in order to prevent curling, the obtained film is 40 to 70
5 hours to 5 days, preferably 45 to 60 ° C 12
By performing the aging treatment for a period of time to 3 days, the curl resistance under the above environment becomes good. In the present invention, 10% by weight based on the total amount of polyester used for film formation.
Other polymers up to a certain degree (for example, polyethylene, polystyrene, polycarbonate, polysulfone, polyphenylene sulfide, polyamide, polyimide, etc.) can be contained. Further, if necessary, additives such as an antioxidant, a heat stabilizer, a lubricant, an antistatic agent, a dye and a pigment may be added.

[0029]

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to the following examples unless it exceeds the gist thereof. The physical property measuring methods used in the present invention are shown below. (1) Average primary particle size The particle size was measured by electron microscopy. The average primary particle diameter was obtained by using the value of 50% of integration (volume basis) in the equivalent spherical distribution of the particles obtained by the measurement. (2) Average secondary particle size Centrifugal sedimentation type particle size distribution analyzer SA- manufactured by Shimadzu Corporation
The particle size was measured by a sedimentation method based on Stokes's resistance law using CP3 type. The value of 50% integrated (volume basis) in the equivalent spherical distribution of the particles obtained by the measurement was used as the average particle diameter. The particle size distribution value (r) was calculated from the following formula. Particle size distribution value (r) = d ₂₅ / d ₇₅ (In the above formula, d ₂₅ and d ₇₅ are the particle volumes corresponding to 25% and 75% of the total volume measured from the large particle side of the cumulative volume of the particle group. Indicates the diameter (μm)

(3) Zeta potential of particles Using a zeta potential measuring device (ELS-800 type, manufactured by Otsuka Electronics Co., Ltd.), particles were added to pure water to prepare a dilute slurry, which was measured by a usual electrophoresis method. (4) Particle dispersibility in polymer After the polymer was cut into an ultrathin section of about 800 Å by an ultrathin film forming apparatus, it was observed with a transmission electron microscope to determine the particle dispersibility in the polymer as follows. ∙ Almost no agglomerated particles are observed × ∙ Aggregated particles are present (5) Melting point Differential calorimeter SSC580DS manufactured by Seiko Instruments Inc.
It measured using C20 type. That is, sample film 1
0 mg was set in a DSC apparatus, the temperature was raised at a rate of 10 ° C./min, the temperature was measured in the range of 0 to 300 ° C., and the melting point was measured as the peak of the melting endothermic peak.

(6) Heat Shrinkage Stress (F) The film was cut into a strip having a width of 10 mm, one end was set on the chuck of the load detector and the other was set on the fixed chuck, and the gap between the chucks was set to 50 mm. The film was immersed in a water bath at 80 ° C. without applying an initial load, and the stress value was measured 10 seconds after the start of immersion. Five points were measured in each of the longitudinal direction and the transverse direction of the film, the heat shrinkage stress (g / mm ² ) was calculated from the cross-sectional area of the film before immersion, and the average value was calculated. (7) Heat shrinkage rate (S) The sample is heat-treated in an oven kept at 80 ° C. in a tensionless state for 10 minutes, the length of the sample before and after that is measured, and the heat shrinkage rate (%) is calculated by the following formula. ) Was calculated. F = (sample length before heat treatment-sample length after heat treatment)
× 100 / (Sample length before heat treatment) Five points were measured in the longitudinal direction and the transverse direction of the film, and an average value was obtained.

(8) Center line average roughness (Ra) According to the method described in Japanese Industrial Standard JIS B0601, a surface roughness measuring device (SE-3 manufactured by Kosaka Laboratory Ltd.)
The center line average roughness (Ra) was determined using F). The tip radius of the stylus was 2 μm, the load was 30 mg, and the cutoff value was 0.08 mm. (9) Practical characteristics of heat-sensitive stencil printing base paper Washi paper was attached to a 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.

Perforation sensitivity ⊙: Predetermined perforation is surely performed and the size of perforation is sufficient and very good ○ ... Predetermined perforation is almost certainly performed and the size of perforation is sufficient Δ ... Rarely 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 sizes of the perforations are 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.

Printing quality ⊙: Clear printing is possible without uneven density and bleeding.
Very good ○: No unevenness in density, bleeding, clear printing, good Δ: Slight unevenness in density, bleeding is recognized, and a little lack of sharpness ×: Conspicuous unevenness in density, bleeding, or blurring Printing durability ○… Continuous printing of 2000 sheets or more is possible ×… Continuous printing of only a few hundred sheets

Example 1 [Production of crosslinked polymer particles] 1500 parts by weight of demineralized water, 0.5 parts by weight of water-soluble polymerization initiator potassium persulfate, and sodium lauryl sulfate as a dispersion stabilizer (trade name: Emal)
0 Kao Co., Ltd.) 0.025 parts by weight was added and uniformly dissolved, and then ethylene glycol dimethacrylate 6 was added.
A mixed solution of 0 parts by weight, 20 parts by weight of methyl methacrylate and 20 parts by weight of divinylbenzene was added. The polymerization reaction was carried out at 70 ° C. for 24 hours while stirring under a nitrogen gas atmosphere. The reaction rate was 98% and the average particle size of the obtained particles was 1.2.
μm, the particle size distribution value (r) is 1.23, and the weight reduction rate is 5.
It was 2%. The zeta potential of the obtained particles is -2.
At 0 mV, the pH at that time was 6.0. When the obtained particles were observed with an electron microscope, they were almost spherical.

Then, 50 parts by weight of δ-type alumina particles having a primary particle size of 18 nm was added to 500 parts by weight of demineralized water and homomixed and dispersed, and then ethyl acid phosphate 0.5 was added.
By adding parts by weight, the pH was adjusted to 5.0, and the mixture was crushed by a sand grinder and filtered to obtain an aqueous slurry containing the particles. The average secondary particle diameter of the obtained particles was 0.04 μm, and the zeta potential was +30 mV. Next, 1600 parts by weight of the above-mentioned cross-linked polymer particle-containing water slurry and 550 parts by weight of δ-type alumina particle-containing water slurry were added and kept under stirring for -4 hours to coat the surface of the cross-linked polymer particles with δ-type alumina particles. . 1500 parts of ethylene glycol was added to the water slurry, and water was distilled off under reduced pressure with heating to obtain an ethylene glycol slurry. When the particles in the slurry were observed with an electron microscope, it was found that almost all the surfaces of the crosslinked polymer particles were covered with alumina particles.

[Production of Polyester-A] 80 parts by weight of dimethyl terephthalate, 20 parts by weight of dimethyl isophthalate and 60 parts of ethylene glycol were used as starting materials, and 0.09 part by weight of magnesium acetate / tetrahydrate was used as a catalyst in a reactor. Then, the reaction start temperature was set to 150 ° C., the reaction temperature was gradually raised with the evaporation of methanol, and after 3 hours,
℃ was made. After 4 hours, 22 parts by weight of the above ethylene glycol slurry containing 1.0 part by weight of the aluminum oxide-treated composite crosslinked polymer particles was added to the reaction mixture which had been substantially subjected to the transesterification reaction, and ethyl acid phosphate was added. Fate 0.04 parts, antimony trioxide 0.0
4 parts was added and the polycondensation reaction was carried out for 4 hours. That is,
The temperature was gradually raised from 230 ° C to 280 ° C. On the other hand, the pressure is gradually reduced from normal pressure and finally 0.3 mm
It was Hg. After 4 hours from the start of the reaction, the reaction was stopped and the polymer was discharged under nitrogen pressure. The intrinsic viscosity of the obtained polyester was 0.75, and when the particles in the polymer were observed with a transmission electron microscope, it was observed that the surface layer of the crosslinked polymer particles was covered with δ-type alumina particles, The dispersibility was extremely good.

[Production of Polyester-B] 100 parts by weight of dimethyl terephthalate, 56 parts by weight of 1,4-butanediol and 0.005 parts by weight of tetrabutyl titanate were placed in a reactor, the reaction starting temperature was set to 150 ° C., and methanol was added. The reaction temperature was gradually raised with the evaporation, and after 3 hours, 21
It was set to 0 ° C. After 4 hours, tetrabutyl titanate 0.0
After adding 05 parts by weight, a polycondensation reaction was carried out for 4 hours. That is, the temperature was gradually raised from 210 ° C to 260 ° C. On the other hand, the pressure is gradually reduced from normal pressure, and finally becomes 0.
It was set to 3 mmHg. After 4 hours from the start of the reaction, the reaction was stopped and the polymer was discharged under nitrogen pressure. The intrinsic viscosity of the obtained polyester was 0.90.

[Production of polyester film and base paper for thermal stencil printing] 50 parts by weight of polyester-A and 50 parts by weight of polyester-B were uniformly blended to obtain 265.
Extruded in sheet form from extruder at 30 ℃, surface temperature is 30 ℃
By using the electrostatic cooling method to rapidly cool and solidify with the rotary cooling drum set to, a substantially amorphous sheet having a thickness of 15 μm was obtained. The obtained sheet is 3.5 times in the longitudinal direction at 65 ° C,
The film was stretched in the transverse direction 3.7 times at 70 ° C and then at 90 ° C for 6 times.
Heat treatment was performed for seconds to produce a biaxially oriented film having a thickness of 1.5 μm. The melting point of the obtained film is 211 ° C and 22.
It was 3 ° C. Then, the obtained film is subjected to a conventional method,
It was attached to a porous thin paper and subjected to an aging treatment at 50 ° C. for 24 hours to prepare a heat-sensitive stencil printing base paper, which was imprinted.

Example 2 A heat-sensitive stencil printing base paper was prepared in the same manner as in Example 1 except that the amount of δ-type alumina particles was 30 parts by weight, and was imprinted.

Example 3 A heat-sensitive stencil printing base paper was prepared in the same manner as in Example 1 except that 50 parts by weight of γ-type alumina particles having an average primary particle diameter of 12 nm were used, and imprinting was performed. At that time, the obtained γ
The average secondary particle diameter of the type alumina particles was 0.07 nm.

Example 4 1.0 part by weight of water-soluble polymerization initiator potassium persulfate and 0.051 part by weight of sodium lauryl sulfate (trade name: Emer 0 Kao Co., Ltd.) as a dispersion stabilizer. Except for the above, a heat-sensitive stencil printing base paper was prepared in the same manner as in Example 1 and was imprinted. At that time, the average particle diameter of the obtained crosslinked polymer particles was 0.8 μm, and the r value was 1.20.

Comparative Example 1 A heat-sensitive stencil printing base paper was prepared in the same manner as in Example 1 except that the δ-type alumina particles were not used, and was imprinted.

Comparative Example 2 A heat-sensitive stencil printing base paper was prepared in the same manner as in Example 1 except that the δ-type alumina particles were replaced with fine silica particles having an average primary particle size of 11 nm, and the imprinting was performed. went.

Comparative Example 3 Example 1 was repeated except that the δ-type alumina particles were replaced by fine titanium oxide particles having an average primary particle size of 27 nm.
A stencil sheet for heat-sensitive stencil printing was prepared in the same manner as described in (1), and was mimetically printed.

Comparative Example 4 For heat-sensitive stencil printing in the same manner as in Example 1 except that the crosslinked polymer particles surface-treated with δ-type alumina particles of Example 1 were replaced with silica particles having an average particle size of 1.2 μm. The base paper was made and the copy was printed. The physical properties and practical properties of the base paper thus obtained are summarized in Table 1 below.

[0047]

[Table 1]

[0048]

According to the film of the present invention, a high-sensitivity heat-sensitive stencil printing base paper having excellent curl resistance, perforation sensitivity, image resolution during printing and printing durability is provided, and its industrial value is high.

Claims (1)

[Claims] 1. The surface of crosslinked polymer particles having an average particle diameter of 0.3 to 3 μm and a particle size distribution value (r) of 1.5 or less has a Mohs hardness of 7 or more, an average primary particle diameter of 5 to 100 nm, and an average. A polyester film comprising 0.1 to 2% by weight of composite crosslinked polymer particles obtained by treating with fine particles having a secondary particle size of 0.2 μm or less, a melting point of 150 to 240 ° C., and a thickness of 0. A polyester film for high-sensitivity heat-sensitive stencil printing base paper, which has a thickness of 0.5 to 3 μm.