JPH1170757A - Film for base paper for heat-sensitive stencil printing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a film for base paper for heat-sensitive stencil printing which enables the remarkable improvement of sensitivity and resolution and also the clear makeup and printing of a character and a solid print form. SOLUTION: This film is composed of a biaxially oriented polyester film and has a film thickness (d) range of 0.3-3 μm. In addition, the surface of the film meets formula: SRma/d<=0.7, SSr>=30. In the formula, SRma is the maximum height [μm] of a three-dimensional surface, d is a film thickness [μm], and SSr is the area percentage % of a center face.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film for a heat-sensitive stencil sheet which is made by perforating plate by receiving heat from a xenon flash lamp, a thermal head, a laser or the like. More specifically, the present invention relates to a polyester film for heat-sensitive stencil printing paper having excellent piercing properties and sharpness during printing.

[0002]

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

However, these conventional heat-sensitive stencil base papers have the following disadvantages. 1) Light black characters do not appear and gradation is poor. 2) When solid printing is performed, printing unevenness easily occurs. 3) Shading appears on the printed portion, and a clear image cannot be obtained. 4) In addition, unevenness in the thickness of the character occurs partially.

In particular, a polyester resin film having a thickness of about 2 μm is used as a film for heat-sensitive stencil paper made by a thermal head. Heat-sensitive stencil printing is less expensive when printing many sheets than electrostatic copying.
High-speed printing is possible. However, there is a disadvantage that it takes time since the original must be made before the first copy is issued.

[0005] At present, 300 to 400 images are available.
Although dpi is the mainstream, it has become necessary to increase the dot density in order to sharpen the image quality of characters and photographs. For example, 3
In the case of 00 dpi, the size of the hole to be pierced is about 80 μm per dot, but when this is 600 dpi, the size of the hole is halved to about 40 μm. These holes are perforated by the heat from the heat generating elements of the thermal head.However, when trying to print a high-density heat-sensitive stencil paper using a conventional film, the size and shape of the holes are insufficient. Printing becomes unclear, and if the energy of the thermal head is increased unnecessarily, the holes are too wide and the adjacent holes are connected, and excessive ink is transferred at the time of printing, characters are blurred, and gradation of photographs etc. Sex was inadequate.

[0006]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned drawbacks, to provide clear and high gradation in both character printing and solid printing without printing unevenness, to shorten plate making time, and to reduce dot density. The object of the present invention is to stably provide a heat-sensitive stencil sheet capable of performing high-quality printing.

[0007]

Means for Solving the Problems The present inventors have conducted intensive studies to eliminate the above-mentioned drawbacks, and as a result, have found that a specific heat-sensitive stencil sheet is suitable, and have completed the present invention. That is, the film for heat-sensitive stencil printing paper according to the present invention has a biaxially oriented polyester film portion as a component, and the thickness d of the polyester film portion is as follows.
In the range of 0.3 to 3 μm, the surface of the film portion satisfies the expressions (1) and (2). SRma / d ≦ 0.7 (1) SRma: three-dimensional maximum surface height [μm] d: film thickness [μm] SSr ≧ 30 (2) SSr: center area ratio [%]

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, the thickness of a polyester film portion is 0.3 to 3 .mu.m. However, the thickness in this case is the thickness of the averaged portion of the uneven portion of the film or the average flat portion. In the case of a thin film as in the present invention, since the ratio of the unevenness of the film surface to the thickness is large, when the measurement is performed with a micrometer, for example, the thickness is measured at the highest portion of the film projection. In the present invention, for example, the thickness of a film whose film density is known may be obtained by the following formula: thickness d = [weight w] / [surface area S] / [density ρ] You may. Alternatively, the cross section of the base paper may be cut out, the film portion may be directly observed with an optical microscope or an electron microscope, and the actual thickness of the film excluding the projections on the surface may be measured.
If the thickness exceeds 3 μm, the perforation of the film becomes insufficient, and if the thickness is less than 0.3 μm, the adjacent holes that have been perforated are connected, or the film portion is rubbed during printing, so that printing is performed. This may cause bleeding or show-through, and uneven printing may easily occur due to the unevenness of the surface of the porous support.

In the present invention, the polyester is a polyester comprising dibasic acid and glycol as constituent components,
Examples of aromatic dibasic acids include terephthalic acid, isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, diphenylsulfondicarboxylic acid, diphenylether dicarboxylic acid, diphenoxyethanedicarboxylic acid, cyclohexanedicarboxylic acid, diphenyldicarboxylic acid, diphenylthioetherdicarboxylic acid, diphenyl Ketone dicarboxylic acid, phenylindane dicarboxylic acid, sodium sulfoisophthalic acid, dibromoterephthalic acid, and the like can be used. As the alicyclic dibasic acid, cyclohexanedicarboxylic acid, decalindicarboxylic acid, hexahydroterephthalic acid and the like can be used. Further, as the aliphatic dibasic acid, oxalic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, dimer acid and the like can be used. As the glycol, ethylene glycol, propylene glycol, tetramethylene glycol, hexamethylene glycol, neopentyl glycol, diethylene glycol and the like can be used as aliphatic diols, and as the aromatic diol, naphthalene diol,
2,2-bis (4-hydroxydiphenyl) propane,
Examples thereof include 2,2-bis (4-hydroxyethoxyphenyl) propane, bis (4-hydroxyphenyl) sulfone, hydroquinone, and tetrabromobisphenol A. As the alicyclic diol, cyclohexanedimethanol, cyclohexanediol, and the like are used. it can.

Further, within a range where the polyester is substantially linear, a polyfunctional compound having three or more functional groups, for example, 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. Polyethers such as polyethylene glycol and polytetramethylene glycol and aliphatic polyesters represented by polycaprolactone may be copolymerized.

[0011] Two or more polyesters may be blended. For example, if 50% or more of the polyester is used, other than polyester may be blended.

In the present invention, there is a great feature in the surface condition of the film portion of the heat-sensitive stencil sheet. Specifically, assuming that the three-dimensional surface maximum height is SRma [μm] and the film thickness is d [μm], SRma / d is 0.7 or less, preferably 0.65 or less, and more preferably 0 or less. .6
0 or less. Also, the center plane area ratio SSr is 30% or more, preferably 35% or more, and more preferably 40% or more.
That is all.

The surface characteristics are specified, for example, in JP-A-2-307788 and JP-A-3-20869.
Although it can be seen in Japanese Patent Publication No. 0 and the like, it was merely defined by one-dimensional surface roughness and the number of protrusions. Japanese Patent Application Laid-Open No. 63-286396 discloses the relationship between the thickness of a film and the size of a particle, but does not mention the surface condition of the film as viewed in the plane. In the flow of high image quality, if the dot density becomes 600 dpi, the size of the heating element portion per dot in the thermal head becomes about 42 μm or less. That is,
In order to enhance the perforability, we have found that the thermal head in a micro area of about 40 μm and the three-dimensional surface condition of the film to be perforated are closely related. Also, in general, the thinner the film portion, the higher the perforation sensitivity is, that is, the perforation can be performed with less energy.However, the thinner the film thickness, the more efficiently the perforation can be performed with less energy. It has been found that there is a close relationship between thickness and surface condition.

For example, when SRma / d exceeds 0.7, the perforation sensitivity is greatly reduced, and a sufficient perforation area cannot be obtained. Even if the energy of the thermal head is increased, adjacent holes are connected. Comes out. Further, when the center plane area ratio SSr is less than 30%, that is, since the area of the uneven portion on the film surface is increased, the thermal efficiency from the thermal head to the film is deteriorated, the perforation sensitivity is significantly reduced, and the perforation is insufficient. Becomes

In the present invention, in order to set the surface morphology of the film to the above-mentioned preferred range, a master polymer containing inert particles is produced as a thermoplastic resin to be extruded in the production method described later, and It is desirable to blend with the polymer. In this case, the master polymer has a melting point higher by 0 to 100 ° C., preferably 20 to 80 ° C. than that of the main component polymer, and / or has a limiting viscosity of 0.1 to 100 ° C.
Those that are 2 to 1 higher are preferred. It is preferable that the main polymer and the master polymer have a certain degree of compatibility with each other.

Further, it is needless to say 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, the vertical and horizontal stretching conditions, the heat setting temperature conditions, and the like.

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

The average particle diameter of the inert particles is as follows:
Preferably it is 0.1 to 3 μm.

Further, the master chip concentration of the inert particles is preferably 0.5 to 10% by weight, more preferably 1 to 7% by weight, from the viewpoint of forming a specific surface morphology.

The concentration of inert particles in the heat-sensitive film also varies depending on the particle type, particle size, etc., but is 0.05 to 2% by weight.
It is preferably from 0.1 to 1% by weight for obtaining a specific surface morphology.

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

Incidentally, the film may have a structure of two or more layers, and inert particles or other additives may be added to one of the layers. In that case, each layer may be co-extruded, or may be formed into a film by an extrusion lamination method or a coating method.

The melting point of the polyester film in the present invention is preferably 230 ° C. or less, more preferably 220 ° C.
Or less, more preferably 210 ° C. or less. In order to pierce the film portion with the heat of the thermal head, the film portion must first be melted by heat, and therefore it is desirable that the film portion has a low melting point. When several polyesters are blended, a plurality of melting points may be detected. In such a case, the melting peak on the lower temperature side may be 230 ° C. or less.

It is desirable that the heat shrinkage of the film portion in the present invention has a specific value at 100 ° C. or 65 ° C.

The heat shrinkage at 100 ° C. has a relationship with the perforation sensitivity, and is considered to indicate the ease of expansion of the holes formed by the film being melted by the heat of the thermal head. The heat shrinkage at 100 ° C. is preferably 5% or more in both the vertical and horizontal directions, more preferably 7% or more, and further preferably 9% or more. If the heat shrinkage is less than 5%, a sufficient perforation diameter cannot be obtained and printing becomes insufficient.

The heat shrinkage at 65 ° C. is related to the curl of the printing base paper. Since the printing base paper of the present invention has a two-layer structure of a film portion and a porous support, the printing base paper is easily curled when the film side changes in size. When the curl becomes large, the handling of the printing base paper is deteriorated, the transferability of the base paper in the stencil printing machine becomes poor, and the base paper becomes jammed. Curling occurs due to distortion when the film and the porous support are laminated, or occurs during storage at room temperature or during transportation. To suppress this curl, 6
The 5 ° C. heat shrinkage is preferably 2% or less, more preferably 1.5% or less, and further preferably 1% or less. In order to improve the transportability of the base paper, it is better to reduce the curl in the vertical direction. Therefore, the heat shrinkage at 65 ° C. is preferably particularly small in the vertical direction.

Next, a 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 supplied to an extruder, and are heated and melted to a temperature equal to or higher than the melting point of the polymer. Then
The molten polymer is extruded from a slit-shaped T-die,
The film is tightly adhered to the cooling roll to obtain a cast film. In order to improve the adhesion between the molten sheet and the cooling roll, a normal electrostatic application adhesion method and / or a liquid surface application adhesion method are preferably employed. The film is further biaxially stretched. Preferably, it is above the glass transition temperature of the polymer, for example 40
2.3 to 7 in the longitudinal direction with a group of rolls heated to
The film is stretched twice, and then stretched 3 to 7 times in the transverse direction, preferably at 45 to 110 ° C.

It is to be noted that a method in which unidirectional stretching is performed in two or more stages can be used, but also in this case, it is preferable that the final stretching ratio falls within the above range. It is also possible to simultaneously biaxially stretch the cast film so that the area magnification becomes 6 to 30 times.

The film thus obtained is subjected to a heat treatment. If necessary, the film may be stretched in the longitudinal and / or transverse directions again before or after the heat treatment. Heat treatment temperature is 90
To 180 ° C., preferably 90 to 150 ° C., and the heat treatment time is usually 1 second to 5 minutes. The heat shrinkage can be adjusted under these heat treatment conditions. The cooling rate of the film after the heat treatment also affects the heat shrinkage characteristics. For example, after the heat treatment, the heat shrinkage stress can be adjusted by rapidly or slowly cooling the film or providing an intermediate cooling zone. In addition, in order to impart a specific heat shrinkage property, the film may be relaxed in the longitudinal direction and / or the transverse direction during the heat treatment or in the subsequent slow cooling zone.

The film can be coated if necessary. In the case of the present invention, a film may be provided with a release layer to impart stick preventing properties and adhesion to a document, or may impart adhesive properties to a porous support and antistatic properties. As the coating solution, a solution dissolved, emulsified or suspended in water is used in terms of explosion-proof property and environmental pollution. The coating layer may be applied to a biaxially stretched film after the completion of the crystal orientation or may be applied to the film before the completion of the crystal orientation and then stretched.However, the latter method is used in order to more remarkably exert the effects of the present invention. Is particularly preferred. The application method is not particularly limited, but application is preferably performed using a roll coater, a gravure coater, a reverse coater, a kiss coater, a bar coater, or the like.

Before the coating, the surface to be coated may be subjected to a corona discharge treatment in air or other various atmospheres if necessary.

In the coating layer of the present invention, an antifoaming agent, a coating crosslinker, a thickener, an organic lubricant,
Inorganic particles, antioxidants, ultraviolet absorbers, foaming agents, dyes, pigments and the like may be contained.

Further, if necessary, inorganic particles may be added to the coating layer. As a typical example, the average particle diameter is preferably 1 μm or less, more preferably 0.5 μm or less.
The following, particularly preferably 0.2 μm or less, specifically, kaolin, silica, silica sol, calcium carbonate,
Titanium oxide, barium salt, alumina, molybdenum sulfide,
Carbon black, zirconium, etc. can be used,
It is not limited to these.

The biaxially stretched thermoplastic film may be obtained by separating the film of the present invention from a laminated film of another thermoplastic polymer (II) having excellent releasability. By doing so, a thin film can be stably formed. The polymer (II) is any polymer selected from polyolefins, polyphenylene sulfides, fluoropolymers and the like.

The layer (II) has a peeling force of 10 g / cm or less, preferably 0.1 to 0.1 g / cm, when peeling from the film (I) of the present invention.
The effect of the present invention is remarkable when it is in the range of 2 g / cm, more preferably in the range of 0.2 to 0.8 g / cm. If the peeling force is too small, peeling between film layers occurs during stretching or film transport, uniform stretching cannot be performed, the film wraps around the stretching roll, the film peels off during film transport, and wrinkles, tears, etc. 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 is broken or a pinhole is formed. Therefore, in order to keep the peeling force within the above range, 0.001 to 1% by weight, preferably 0.005 to 0.5% by weight of a non-particulate lubricant is contained in the polymer, especially in the (II) layer. It is good to be.

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

Specific examples of the non-particulate lubricant include: (1) aliphatic hydrocarbons liquid paraffin, microcrystalline wax, natural paraffin, synthetic paraffin, polyethylene wax,
Such as polypropylene wax.

(2) Higher fatty acids or metal salts thereof Stearic acid, calcium stearate, hydroxystearic acid, hydrogenated oil, sodium montanate, etc.

(3) Aliphatic amides Stearamide, oleamide, erucamide, ricinoleamide, behenamide, methylenebisstearamide and the like.

(4) Fatty acid ester n-butyl stearate, methylhydroxystearate, myristyl celloate, polyhydric alcohol fatty acid ester, ester wax and the like.

(5) Fatty acid ketone Ketone wax and the like.

(6) Fatty alcohols 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 alkyl amide, polyoxyethylene fatty acid ester and the like.

(9) Silicon oil Linear methyl silicone oil, methylphenyl silicone oil, modified silicone oil and the like.

(10) Fluorosurfactants Fluoroalkylcarboxylic acid, perfluoroalkylcarboxylic acid, monoperfluoroalkylethyl phosphate, perfluoroalkylsulfonic acid salt, etc.

In addition, inorganic fine particles having an average particle diameter 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 non-particle-based lubricant. , Titanium oxide, alumina, zirconia, aluminum hydroxide, etc. in the (I) layer and / or (II) layer.
When the content is 1 to 0.5% by weight, the effect of the non-particulate lubricant can often be synergistically enhanced.

The polyester film thus obtained can be used as a heat-sensitive stencil sheet by laminating a predetermined porous support with a known adhesive in a conventional manner.

In the step of manufacturing a film,
The porous support may be attached to a non-stretched film or a uniaxially stretched film and stretched at the same time, or the porous support may be laminated and wound at the stage of biaxially stretching the film.

In order to reduce the curl of the printing base paper of the present invention, the film is kept in a roll state at 40 to 60 ° C. for 3 hours to 7 hours.
Aging treatment may be performed at 45 to 55 ° C. for 10 days to 4 days.

[Method for Measuring Physical Properties and Method for Evaluating Effect] The characteristic values of the present invention are based on the following measuring methods and evaluation criteria. (1) Glass transition temperature, cold crystallization peak temperature, melting point, crystal melting energy (ΔHu) 10 mg of polyester was set in a differential scanning calorimeter (DSC-2, manufactured by PERKIN ELMER) at 20 ° C./nitrogen stream. The temperature was raised at a rate of min, and the average value of the temperature at which the baseline began to be biased and the temperature at which it returned to a new baseline was taken as the glass transition temperature. The apex of the exothermic peak due to crystallization was defined as the cold crystallization peak temperature, and the apex of the crystal melting endothermic peak was defined as the melting point. For the crystal melting energy of polyester and polyester film, first, the area a of the crystal melting endothermic peak was determined, indium was measured under the same DSC measurement conditions, and this area b = 6.8 ca
1 / g was obtained from the following equation. ΔHu (cal / g) = a / b × 6.8

(2) Heat Shrinkage A film was sampled to a width of 10 mm and a length of 300 mm.
The sample was left to stand in an atmosphere of 60% RH for 30 minutes at a temperature of 60 ° C., and the sample was marked at intervals of about 200 mm in that atmosphere, and the interval between the marks was measured using a linear scale length measuring machine. I do. Next, the sample to be measured is left in a hot-air oven set at a predetermined temperature in a tension-free state for a predetermined time, and then is placed in an atmosphere of 23 ° C. and 60% RH for 1 hour.
After time cooling and humidity control, the interval between the marks previously attached is measured, and the measured value is B. At this time, the heat shrinkage is determined by the following equation. x [%] = 100 (AB) / A The heat treatment was performed at 100 ° C. for 30 minutes and at 65 ° C. for 1 hour.

(3) Practical characteristics of heat-sensitive stencil printing A base paper was prepared by laminating a film of Japanese paper. The obtained base paper is applied with an applied energy of 0.0 by a thermal head.
At 9 mJ and 0.12 mJ, character images and 16-step gradation images were made. The perforated state of the gradation image portion was observed with a microscope from the film side of the pre-processed base paper, and the following items were evaluated.

(I) Perforation sensitivity ：: Predetermined perforation is reliably performed and good. Δ: There are some places where the predetermined perforation cannot be obtained,
No problem in practical use. ×: There are many places where a predetermined perforation cannot be obtained, and there is a problem in practical use.

(Ii) Independent Perforation A: Each dot is independently perforated. Δ: Perforated almost independently, no practical problem. X: The dots between adjacent dots are connected, and there is a problem in practical use.

Further, using the stencil sheet, printing was performed using a lithographic AP7200 printing machine manufactured by Riso Kagaku Kogyo KK, and the following characteristics of the obtained characters and images were visually judged. (Iii) Character printability Character missing / absent Character unevenness / thickness Unavailable in terms of, x mark, and no problem with o mark Available but usable ones are indicated by a triangle.

(Iv) Evaluation of solid printability ● (circle black inside) 0.5, 1.
Plates made and printed using base papers of 0, 3.0, 10.0 and 30.0 mmφ were evaluated as follows. Compatibility with solid paper base paper size
Those that have no problem are indicated by ○, and those that have problems but are usable are indicated by △.

(4) Three-dimensional maximum surface height SRma, center plane area ratio SSr Fine shape measuring device (model: ET-3) manufactured by Kosaka Laboratory Co., Ltd.
0HK), the stylus diameter was 2 μR, the cutoff was 0.25 mm, the measurement length (X direction) was 0.5 μm, the feed pitch in the Y direction was 5 μm, and the number of recordings was 80.

(5) Intrinsic Viscosity The value calculated from the following formula based on the solution viscosity measured in orthochlorophenol at 25 ° C. was used. ηsp / C = [η] + K [η] 2 · C where ηsp = (solution viscosity / solvent viscosity) -1 C: weight of dissolved polymer per 100 ml of solvent (g / 1
K: Huggins constant (0.343) Solution viscosity and solvent viscosity were measured with an Ostwald viscometer.

[0060]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on embodiments. Example 1 Polymerization was carried out by a conventional method using dimethyl terephthalate / dimethyl isophthalate (molar ratio: 80/20) as a dicarboxylic acid component and ethylene glycol as a glycol component, and silica particles having an average particle size of 1.8 μm were added thereto. By adding 0.4% by weight, a copolymerized polyester having an intrinsic viscosity of 0.7 was obtained. The polymer is extruded into a sheet at 275 ° C.
It was cooled and solidified on a rotating cooling drum set at 25 ° C. by using an electrostatic application method. Then, move the film vertically
The film was stretched at 5 ° C. and 4.5 times, at 82 ° C. and 4.4 times in the transverse direction, and further subjected to a heat treatment at 120 ° C. for 5 seconds to produce a biaxially stretched film having a thickness of 2 μm.

Example 2 Polymer A had an intrinsic viscosity of 0.75 and an average particle size of 1.2.
Polyethylene terephthalate containing 1.2% by weight of μm calcium carbonate particles was prepared, and as polymer B, polybutylene terephthalate having an intrinsic viscosity of 0.85 was prepared. 50 parts by weight of polymer A and 50 parts by weight of polymer B are uniformly blended and extruded into a sheet at 270 ° C.
Was cooled and solidified on the rotating cooling drum set in the above by using an electrostatic application method. Then, put the film vertically at 65 ° C.
Stretched 3.5 times, transversely at 72 ° C., 4.0 times, and further 10 times
Heat treatment was performed at 0 ° C. for 5 seconds to produce a biaxially stretched film having a thickness of 1.5 μm. The obtained film was aged in a roll at 48 ° C. for 15 hours.

Example 3 Calcium carbonate particles having an average particle size of 1 μm were polymerized by a conventional method using dimethyl terephthalate / dimethyl isophthalate (molar ratio: 75/25) as a dicarboxylic acid component and ethylene glycol as a glycol component. To 0.
By adding 6% by weight, a copolymerized polyester having an intrinsic viscosity of 0.75 was obtained. This polymer was extruded into a sheet at 270 ° C., and was cooled and solidified on a rotating cooling drum set at 25 ° C. by using an electrostatic application method. Then, the film is stretched at 105 ° C. in the longitudinal direction, 4.5 times, and at 82 ° C. in the transverse direction, 5 times,
Further, heat treatment was performed at 120 ° C. for 5 seconds to produce a biaxially stretched film having a thickness of 1.3 μm.

Example 4 Polymerization was carried out by a conventional method using dimethyl terephthalate / dimethyl isophthalate (molar ratio: 80/20) as a dicarboxylic acid component and ethylene glycol as a glycol component. By adding 0.7% by weight of calcium particles, a copolymerized polyester having an intrinsic viscosity of 0.7 was obtained. This polymer was extruded into a sheet at 275 ° C., and was cooled and solidified on a rotating cooling drum set at 25 ° C. using an electrostatic application method. Next, the film was stretched in the longitudinal direction at 105 ° C., 5 times and in the transverse direction at 82 ° C., 5 times, and then heat-treated at 120 ° C. for 5 seconds to produce a biaxially stretched film having a thickness of 1.5 μm.

Comparative Example 1 The same raw material as in Example 4 was extruded into a sheet at 275 ° C., and was cooled and solidified on a rotating cooling drum set at 25 ° C. by using an electrostatic application method. Then, the film is stretched at 105 ° C. 3.9 times in the longitudinal direction and at 82 ° C. and 3.8 times in the transverse direction, and further subjected to a heat treatment at 120 ° C. for 5 seconds to have a thickness of 1.3.
A μm biaxially stretched film was produced.

Comparative Example 2 Polymer A had an intrinsic viscosity of 0.75 and an average particle size of 2 μm.
A polyethylene terephthalate containing 1.2% by weight of silica particles was prepared.
Thus, polybutylene terephthalate No. 5 was prepared. 50 parts by weight of polymer A and 50 parts by weight of polymer B were uniformly blended, extruded into a sheet at 270 ° C., and cooled and solidified on a rotating cooling drum set at 30 ° C. using an electrostatic application method. Then, the film was stretched in the longitudinal direction at 65 ° C. and 3.5 times, in the transverse direction at 72 ° C. and 3.5 times, and further subjected to a heat treatment at 100 ° C. for 5 seconds to produce a biaxially stretched film having a thickness of 1.5 μm. .

The films obtained in Examples 1 to 4 and Comparative Examples 1 and 2 were laminated on a porous thin paper according to a conventional method to prepare a heat-sensitive stencil sheet, and the characteristics were evaluated by a plate-making / printing machine. It is shown in FIG. As shown in Table 1, excellent printing practical characteristics can be obtained by using the surface characteristics specified in the present invention.

[0067]

[Table 1]

[0068]

According to the film for heat-sensitive stencil printing paper of the present invention, the following excellent effects can be obtained. (1) Clear plate making and printing can be performed for both characters and solid printing. (2) It is possible to make a plate and print with unevenness in thickness and unevenness in shading by printing characters and solid printing. (3) Sensitivity and resolution are significantly improved.

Claims (2)

[Claims] 1. A film comprising a biaxially oriented polyester film, wherein the thickness d of the film is in the range of 0.3 to 3 μm, and the surface of the film satisfies the following formulas (1) and (2). A film for thermosensitive stencil printing paper characterized by the following. SRma / d ≦ 0.7 (1) SRma: three-dimensional maximum surface height [μm] d: film thickness [μm] SSr ≧ 30 (2) SSr: center plane area ratio [%] 2. The melting point of the polyester film is 230 ° C.
Less than 2% at 65 ° C.
2. The polyester film for heat-sensitive stencil printing paper according to claim 1, wherein the heat shrinkage at 0 ° C. is 5% or more.