JP3952595B2 - High sensitivity heat sensitive stencil film - Google Patents

Description

【００６０】
表１から分かるように、本発明に係るフイルムでは、独立穿孔性、文字印刷性、ベタ印刷性にすぐれ、かつ、穿孔感度も十分に実用に供することのできる高感度のものが得られた。
【００６１】
【発明の効果】
以上説明したように、本発明の高感度感熱孔版印刷原紙用フイルムによれば、独立穿孔性がよく、文字印刷及びベタ印刷共に鮮明で階調性が高く、印刷ムラがなく、かつ、製版時間を短くでき、ドット密度のより高い印刷が可能な高感度の感熱孔版印刷原紙を安定して提供することができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a polyester film for thermal stencil printing base paper that is perforated and made by receiving heat from a xenon flash lamp, a thermal head, a laser, or the like, and in particular, high-sensitivity thermal stencil printing excellent in perforation and sharpness during printing. The present invention relates to a polyester film for base paper.
[0002]
[Prior art]
As the 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. As the film for a heat-sensitive stencil sheet, a vinyl chloride / vinylidene chloride copolymer is used. A film, a polypropylene film, a polyethylene terephthalate copolymer film are used, and a thin paper, Tetron or the like has been used as a porous support (for example, JP-A-53-49519).
[0003]
However, these have the following drawbacks.
(1) Black thin characters are difficult to appear and gradation is poor.
(2) When solid printing is performed, uneven printing tends to occur.
(3) The printed portion is shaded and it is difficult to obtain a clear one.
(4) Character thickness unevenness tends to occur partially.
In particular, a polyester-based 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 cheaper when printing many sheets than electrostatic copying, and high-speed printing is possible. However, there is a disadvantage that it takes time because the original must be made before the first copy is made. Therefore, there is a demand for a film for heat-sensitive stencil paper that has better perforation properties and can perform desired perforation in a shorter time.
[0004]
Further, the current image is mainly 300 to 400 dpi, but it has been necessary to increase the dot density in order to make the image quality of characters and photographs clearer. For example, in the case of 300 dpi, the size of the hole to be perforated is about 80 μm per dot, but when this is 600 dpi, the size of the hole is about 40 μm, which is a half. These holes are punched by heat from the heating element of the thermal head. However, when printing high-density stencil paper using conventional film with high dot density, the size and shape of the holes are insufficient. When printing tends to be unclear and the energy of the thermal head is increased unnecessarily, the holes expand too much and the holes next to each other are connected to each other. The tonality was insufficient.
[0005]
[Problems to be solved by the invention]
Therefore, the object of the present invention is to eliminate the above-mentioned drawbacks, and for both character printing and solid printing to be clear and high in gradation, to have no printing unevenness, to shorten the plate making time, and to enable printing with higher dot density. It is to provide a heat-sensitive stencil sheet with high sensitivity.
[0006]
[Means for Solving the Problems]
  In order to solve the above problems, the highly sensitive heat-sensitive stencil film of the present invention is a biaxially stretched polyester film having a thickness of 0.5 to 4 μm,The three-dimensional surface center plane average roughness SRa [nm] of the film surface is 20 <SRa <40,The film is characterized by satisfying the following formula.
[S (Tmax) −Y (Tmax)] + [S (Tmax + 30) −Y (Tmax + 30)] + [S (Tmax + 60) −Y (Tmax + 60)]≧ 160 ・ ・ Formula (1)
Tm-Tmax> 60 [° C.] Formula (2)
here,
Tmax [° C.]: temperature indicating the maximum value of heat shrinkage stress of the film
Tm [° C.]: Melting point of film. However, if there are multiple melting points, the melting point on the lowest temperature side.S (T) [g / mm²]: Thermal shrinkage stress at temperature T [° C]
Y (T) [kg / mm²]: The tensile elastic modulus of the film at a temperature T [° C.].
[0007]
When perforating a heat-sensitive stencil sheet, the film's holes try to expand due to heat shrinkage due to the heat instantaneously applied from the thermal head to the film (although it tries to expand in the direction of increasing the hole) At that time, the rigidity of the film that receives the heat of the thermal head hinders the expansion of the hole. Therefore, it has been found that the larger the difference between the shrinkage force and the elastic force of the film at a certain temperature, the easier the hole can be expanded by the heat shrinkage force against the rigidity of the film, and the desired perforation can be performed in a shorter time. The present invention has been completed.
[0008]
  That is, in the present invention, the heat shrinkage stress S (T) [g at the temperature Tmax [° C.] indicating the maximum value of the heat shrinkage stress of the film, the temperature 30 ° C. higher than Tmax, and the temperature 60 ° C. higher than Tmax. / Mm²] And tensile modulus Y (T) [kg / mm²] And the total difference160 or more as shown in the examples belowOverall, in this temperature range, the heat shrink force of the film overcomes the rigidity of the film, thereby making it easier to widen the hole to be perforated, and in a shorter time So that it can be perforated.
[0009]
As a result of improved perforation, it is possible to increase the energy of the thermal head, and as a result of easily perforating holes of a desired size, it is possible to easily avoid the occurrence of inconveniences such as connection between the holes, Simultaneously with shortening of the punching time, dot size and gradation can be improved.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail together with preferred embodiments.
The highly sensitive heat-sensitive stencil film according to the present invention comprises a biaxially stretched polyester film. In an unstretched film or a uniaxially stretched film, a desired high heat shrinkage stress at a specific temperature cannot be obtained.
[0011]
In the present invention, the polyester is a polyester comprising dibasic acid and glycol as constituent components, and the aromatic dibasic acid includes terephthalic acid, isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, diphenylsulfone dicarboxylic acid, diphenyl ether dicarboxylic acid. Diphenoxyethane dicarboxylic acid, cyclohexane dicarboxylic acid, diphenyl ketone dicarboxylic acid, phenylindane dicarboxylic acid, sodium sulfoisophthalic acid, dibromoterephthalic acid, and the like can be used. As the alicyclic dibasic acid, cyclohexane dicarboxylic acid, decalin dicarboxylic acid, hexahydroterephthalic acid, or the like can be used. 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 the aliphatic diol, and naphthalenediol, 2,2-bis (4- Hydroxydiphenyl) propane, 2,2-bis (4-hydroxyethoxyphenyl) propane, bis (4-hydroxyphenyl) sulfone, hydroquinone, tetraprobisbisphenol A and the like can be used. As the alicyclic diol, cyclohexanedi Methanol, cyclohexanediol, etc. can be used.
[0012]
Further, a polyfunctional compound having three or more functional groups within the range in which the polyester is substantially linear, such as glycerin, trimethylolpropane, pentaerythritol, trimellitic acid, trimesic acid, pyromellitic acid, tricarballylic acid, gallic acid, etc. May be copolymerized, or a monofunctional compound such as o-benzoylbenzoic acid or naphthoic acid may be added and reacted. Further, polyethers such as polyethylene glycol and polytetramethylene glycol, and aliphatic polyesters typified by polycaprolactone may be copolymerized.
[0013]
Two or more kinds of polyesters may be blended. For example, if 50% or more of the polyester is polyester, other than polyester may be blended.
[0014]
  In the biaxially stretched polyester film constituting the film for a high-sensitivity heat-sensitive stencil printing base paper according to the present invention,
[S (Tmax) −Y (Tmax)] + [S (Tmax + 30) −Y (Tmax + 30)] + [S (Tmax + 60) −Y (Tmax + 60)]≧ 160It is necessary to satisfy
here,
    Tmax [° C.]: temperature indicating the maximum value of heat shrinkage stress of the film
    S (T) [g / mm²]: Thermal shrinkage stress at temperature T [° C]
    Y (T) [kg / mm²]: The tensile elastic modulus of the film at a temperature T [° C.].
[0015]
  The value obtained by the above formula isLess than 160In this case, the expansion force of the hole due to heat shrinkage is not sufficient for the rigidity of the film at that temperature, the hole does not expand sufficiently, the printing density is low, and there is a possibility that characters and pictures are faded.
[0016]
Preferably, S (Tmax) −Y (Tmax)> 0 is satisfied at a temperature Tmax [° C.] indicating the maximum value of the heat shrinkage stress of the film. If the value of this equation becomes 0 or less at this temperature Tmax, drilling with lower energy becomes insufficient, resulting in a longer drilling time or poor drilling.
[0017]
  The relationship between the melting point Tm of the film and the above Tmax is
    Tm-Tmax> 60 [° C.]
That it isis necessary.As a result, the meaning of the temperature range including the above (Tmax + 30) [° C.] and (Tmax + 60) [° C.] is generated, and the melting point Tm [° C.] of the film (the temperature on the low temperature side when there are a plurality of Tm) and Tmax [° C. ] Is smaller than 60 ° C., there is a possibility that a sufficient perforation diameter cannot be obtained (a large hole cannot be opened).
[0018]
The melting point Tm [° C.] of this film is preferably lower than 230 ° C. Preferably it is 225 degrees C or less, More preferably, it is 220 degrees C or less. If the melting point of the film is 230 ° C. or higher, there is a possibility that the perforation will be insufficient and the characters will be blurred, the solid part will be thin, or the gradation will be insufficient. In order to perforate the film portion with the heat of the thermal head, the film portion must first be melted by heat. Therefore, it is desirable that the melting point of the film portion is low. When several polyesters are blended, a plurality of melting points may be detected. In this case, the melting peak on the lower temperature side should be 230 ° C. or lower.
[0019]
Thermal contraction stress S (Tmax) at Tmax of film [g / mm²] Is preferably in the range of 300 <S (Tmax) <2000, and more preferably in the range of 500 <S (Tmax) <1500. Thermal contraction stress S (Tmax) is 300 [g / mm²If it is smaller than], the hole does not open. Also, 2000 [g / mm²If it is larger than], there is a possibility that the independent punching property is lost, the characters are blurred, or the ink is excessively printed when the solid printing is performed, thereby causing the show-through.
[0020]
Further, it is desirable that the thermal contraction rate of the film portion in the present invention takes a specific value at 65 ° C. 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 easily curls when the dimensions of the film side change. When the curl becomes large, the handling property of the printing base paper is deteriorated, the transporting property of the base paper in the stencil printing machine becomes poor, and the base paper is clogged. Curling occurs due to distortion when laminating a film and a porous support, or occurs during storage at normal temperature or during transportation. Further, since the master is not uniformly set on the printing plate cylinder portion to be printed, printing spots are likely to appear. In order to suppress this curl, the heat shrinkage rate at 65 ° C. is preferably 2% or less, more preferably 1.5% or less, and further preferably 1.0% or less. In order to improve the transportability of the base paper, it is better to reduce the curl in the longitudinal direction. Therefore, the heat shrinkage rate at 65 ° C. is particularly preferably smaller in the longitudinal direction.
[0021]
  In the present invention, the three-dimensional surface center plane average roughness SRa [nm] of the film surface is 20 <SRa <40.Is necessary,Preferably 20 <SRa <35. When SRa is smaller than 20 [nm], the winding of the film is deteriorated, the productivity is lowered, and wrinkles are caused when laminating with Japanese paper. Furthermore, it is easy to raise a stick when drilling. When SRa is larger than 40 [nm], unevenness in perforation occurs, and characters are likely to become blurred or uneven in printing.
[0022]
The film surface characteristics are defined in, for example, Japanese Patent Laid-Open Nos. 2-3307788 and 3-208690, but are merely defined by one-dimensional surface roughness and the number of protrusions. It was. Japanese Patent Application Laid-Open No. 63-286396 discloses the relationship between the thickness of the film and the size of the particles, but does not mention the surface condition seen in the plane of the film. It can be seen that if the dot density is 600 dpi in the trend of high image quality, the size of the heating element portion per dot in the thermal head is about 42 μm or less. That is, in order to improve perforation property, it has been found that the thermal head in a micro area of about 40 μm and the three-dimensional surface state of the perforated film are closely related. Also, in general, the thinner the film part, the better the perforation sensitivity, that is, it can be perforated with less energy, but the thinner the film thickness, the more efficient it is to perforate with less energy. It was found that there is a close relationship between the thickness and the surface condition of the material. For example, when SRa exceeds 40 [nm], the perforation sensitivity is greatly reduced and a sufficient perforation area cannot be obtained, and even if the energy of the thermal head is increased, adjacent holes are connected. . On the other hand, when SRa is smaller than 20 [nm], as described above, the winding of the film is deteriorated, the productivity is lowered, and wrinkles are caused when laminating with Japanese paper.
[0023]
In the present invention, in order to make the surface form of the film within the above-mentioned preferable range, a master polymer containing inert particles is made as a thermoplastic resin used for extrusion in the production method described later, and blended with the main component polymer. It is desirable. In this case, it is preferable that the master polymer has a melting point higher by 0 to 100 ° C., preferably 20 to 80 ° C. than the main component polymer, and / or has an intrinsic viscosity of 0.2 to 1.0 higher. In addition, the main component polymer and the master polymer are preferably compatible with each other to some extent.
[0024]
Furthermore, it goes without saying that the specific surface morphology can be controlled to some extent by the shear stress during extrusion, the basis weight of the filter, the extrusion conditions, the longitudinal and lateral stretching conditions, the heat setting temperature conditions, and the like.
[0025]
As the inert particles to be included, particles selected from oxides or inorganic salts of elements of group IIA, IIIB, IVA, and IVB, for example, calcium carbonate obtained as a synthetic or natural product, wet silica (silicon dioxide) Dry silica (silicon dioxide), aluminum silicate (kaolinite), barium sulfate, calcium phosphate, talc, titanium dioxide, aluminum oxide, aluminum hydroxide, calcium silicate and the like can be used.
[0026]
The average particle diameter of the inert particles is preferably in the range of 0.1 to 3 μm. Furthermore, the master chip concentration of the inert particles is preferably 0.5 to 10% by weight, and more preferably 1 to 7% by weight from the viewpoint of producing a specific surface form.
[0027]
The inert particle concentration in the heat-sensitive film varies depending on the particle type, particle size, etc., but it is preferably 0.05 to 2% by weight, preferably 0.1 to 1% by weight for obtaining a specific surface form. .
[0028]
In the present invention, an additive having an absorption peak in the wavelength range of flash irradiation may be added to the film. In addition, additives such as an antioxidant, a heat stabilizer, a lubricant, an antistatic agent, a dye, and a pigment may be blended as necessary.
[0029]
The film may have a structure of two or more layers, and insoluble particles and other additives may be added to any layer. In that case, each layer may be coextruded or may be laminated by an extrusion lamination method or a coating method.
[0030]
Next, although the manufacturing method of the polyester film which concerns on this invention is demonstrated, it is not limited to this example.
The dried polymer chip is supplied to an extruder, heated to a temperature equal to or higher than the melting point of the polymer, and melted. Next, the molten polymer is extruded from a T-die having a slit-like discharge port, and is tightly solidified on a cooling roll to obtain a cast film. In order to improve the adhesion between the molten sheet and the cooling roll, it is usually preferable to employ an electrostatic application adhesion method and / or a liquid surface application adhesion method. The cast film is further stretched biaxially. Preferably, it is stretched 2.3 to 7 times in the longitudinal direction (longitudinal direction) with a group of rolls heated above the glass transition temperature of the polymer, for example 40 to 120 ° C., and then preferably 45 to 120 in the width direction (transverse direction). Stretch 3 to 7 times at ° C. In addition, although the method of extending | stretching one direction in two steps or more can be used, it is preferable that the final draw ratio also falls in the said range also in that case. The cast film can be simultaneously biaxially stretched so that the area magnification is 6 to 30 times.
[0031]
The film thus obtained is heat-treated, and may be stretched again in the longitudinal and / or transverse direction before or after the heat treatment, if necessary. The heat treatment temperature is 70 to 180 ° C., preferably 80 to 150 ° C., and the heat treatment time is usually 1 second to 5 minutes. The heat shrinkage characteristics can be adjusted under these heat treatment conditions. In addition, 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. Moreover, in order to give a specific heat shrink characteristic, you may relax in the vertical direction and / or the horizontal direction during the heat treatment or in the subsequent slow cooling zone.
[0032]
The film can be coated as necessary. In the case of the present invention, by providing a release layer on the film, it is possible to impart sticking prevention properties and adhesion prevention properties to a document, or to provide adhesion to a porous support and antistatic properties. As the coating solution, a solution which is dissolved in water, emulsified or suspended in view of explosion proof and environmental pollution is used. The coating layer has a method of coating on a biaxially stretched film after completion of crystal orientation or a method of stretching after coating on a film before completion of crystal orientation, but the latter method is used in order to exhibit the effects of the present invention more remarkably. Is particularly preferred. The method of applying is not particularly limited, but it is preferable to apply using a roll coater, gravure coater, reverse coater, kiss coater, bar coater or the like. Moreover, you may corona-discharge-process in the air | atmosphere other various atmosphere before application | coating as needed before apply | coating.
[0033]
In the coating layer in the present invention, an antifoaming agent, a coating crosslinker, a thickener, an organic lubricant, inorganic particles, an antioxidant, an ultraviolet absorber, a foaming agent, a dye, and a pigment are used as necessary. Etc. may be included.
[0034]
Further, if necessary, inorganic particles may be added to the coating layer. If a typical example is given, the average particle size is preferably 1 μm or less, more preferably 0.5 μm or less, particularly preferably 0.2 μm. The following can be used, specifically kaolin, silica, silica sol, calcium carbonate, titanium oxide, barium salt, alumina, molybdenum sulfide, carbon black, zirconium, etc., but are not limited thereto. .
[0035]
Moreover, the film according to the present invention may be peeled and decomposed from a laminated film with another thermoplastic polymer (II) excellent in peelability to obtain a biaxially stretched polyester. By carrying out like this, a thin film can be formed stably. The polymer (II) is any polymer selected from polyolefin, polyphenylene sulfide, fluorine polymer and the like.
[0036]
The (II) layer has a peeling force of 10 g / cm or less, preferably 0.1 to 2 g / cm, more preferably 0.2 to 0.8 g / cm when peeling from the film (I) of the present invention. Preferably there is. If the peeling force is too small, peeling between film layers will occur during stretching and film transport, and uniform stretching will not be possible, the film may be wrapped around the stretching roll, or the film may be peeled off during film transport, causing wrinkles and tearing. May occur. On the other hand, if the peeling force is too large, the film cannot be peeled at a high speed, and the film may be torn or a pinball may be generated. 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 non-particulate lubricant is contained in the polymer, particularly (II) layer. It is good to be.
[0037]
The non-particulate lubricant is a substance having a melting point or a softening temperature of 200 ° C. or less, even if it is liquid at normal temperature or solid at normal temperature, and may be any film that provides film lubricity. It is a substance like this.
[0038]
In addition, when two or more types of these substances are contained in the film, the total amount of them may be within the above content range.
[0039]
Specific examples of non-particulate lubricants include
(1) Aliphatic hydrocarbon
Liquid paraffin, microcrystalline wax, natural paraffin, synthetic paraffin, polyethylene wax, polypropylene wax, etc.
(2) Higher fatty acids or their metal salts
Stearic acid, calcium stearate, hydroxystearic acid, hydrogenated oil, sodium montanate, etc.
(3) Aliphatic amide
Stearamide, oleamide, erucamide, ricinoleamide, behenamide, methylenebisstearamide, etc.
(4) Fatty acid ester
n-butyl stearate, methyl hydroxystearate, myricyl cellotinate, polyhydric alcohol fatty acid ester, ester wax and the like.
(5) Fatty acid ketone
Ketone wax.
(6) Fatty acid alcohol
Lauryl alcohol, stearyl alcohol, myristyl alcohol, cetyl alcohol, etc.
(7) Partial esters of fatty acids and polyhydric alcohols Glycerin fatty acid esters, hydroxystearic acid triglycerides, sorbitan fatty acid esters, and the like.
(8) Nonionic surfactant
Polyoxyethylene alkyl ether, polyoxyethylene phenyl ether, polyoxyethylene alkylamide, polyoxyethylene fatty acid ester and the like.
(9) Silicone oil
Linear methyl silicone oil, methylphenyl silicone oil, modified silicone oil, etc.
(10) Fluorosurfactant
Fluoroalkyl carboxylic acid, bar fluoroalkyl carboxylic acid, monoperfluoroalkylethyl phosphoric acid ester, perfluoroalkyl sulfonate, etc.
[0040]
In addition, as the non-particulate lubricant, 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, titanium oxide, alumina, When the zirconia, aluminum hydroxide and the like are contained in the (I) layer and / or (II) layer in an amount of 0.01 to 0.5% by weight, the effect of the non-particulate lubricant may be increased synergistically. Many.
[0041]
The polyester film thus obtained can be used as a heat-sensitive stencil base paper by laminating a predetermined porous support using a known adhesive according to a conventional method.
[0042]
In the process of producing the film, the porous support may be bonded to an unstretched film or a uniaxially stretched film and stretched at the same time, or the porous support is bonded at the stage of biaxially stretching the film. You may wind up.
[0043]
In order to reduce the curl of the printing base paper of the present invention, the film may be aged at 40 to 60 ° C. for 3 hours to 7 days, preferably at 45 to 55 ° C. for 10 hours to 4 days in a roll state.
[0044]
[Measurement method of physical properties]
Below, the measuring method of the physical property used for prescription | regulation and evaluation of this invention is demonstrated.
(1) Thermal contraction stress
The film was cut into a sample width of 10 mm and a length of 10 cm, and the chucking force was 50 mm. The shrinkage force generated when heated at a heating rate of 10 ° C./min from room temperature with a heat shrinkage stress measuring machine manufactured by Nishiyama Seisakusho The shrinkage stress with respect to temperature was measured. The initial load was 1 g, and the cross-sectional area value of the film before raising the temperature was used when obtaining the stress.
[0045]
(2) Three-dimensional surface center plane average roughness SRa
Made by Kosaka Laboratory Co., Ltd., using a fine shape measuring instrument (model: ET-30HK), stylus diameter cone type 2 μR, cutoff 0.25 mm, measurement length (X direction) 0.5 μm, Y direction feed The pitch was 5 μm and the number of records was 80.
[0046]
(3) Melting point
10 mg of polyester was set in a differential scanning calorimeter (DSC-2 type) manufactured by PERKIN ELMER, and the temperature was raised at a rate of 20 ° C./min under a nitrogen stream, and the peak of the crystal melting endothermic peak was taken as the melting point. .
[0047]
(4) Thermal contraction rate
Take a film 10 mm wide and 300 mm long, leave it in an atmosphere of 23 ° C. and 60% RH for 30 minutes, and mark the sample to be measured at an interval of about 200 mm in that atmosphere. The interval between the marks is measured and the value is A. Next, the sample to be measured is heat-treated in a hot air oven set at a temperature of 65 ° C. for 1 hour in a tension-free state, then cooled and conditioned in an atmosphere of 23 ° C. and 60% RH for 1 hour. Measure the distance between the first marks and let B be the measured value. At this time, the thermal contraction rate x is obtained by the following equation.
x [%] = 100 (A−B) / A
[0048]
(5) Tensile modulus
The film was cut into a sample width of 10 mm and a length of 15 cm, and measured with a tensile tester at a tensile speed of 10 mm / min with a chuck spacing of 100 mm. The tensile elastic modulus was calculated from the tangent of the rising portion of the obtained load-elongation curve. In the measurement, a small oven was set at a predetermined temperature in advance, and the oven was moved to the sample portion sandwiched between the chucks of the tensile tester, and the tensile was started 10 seconds later.
[0049]
(6) Practical characteristics of thermal stencil printing
A base paper was made by laminating film and Japanese paper. A letter image and a 16-step gradation image were made on the obtained base paper with a thermal head at an applied energy of 0.09 mJ and 0.12 mJ. The perforated state of the gradation image portion was observed with a microscope from the film side of the plate-making base paper, and the following items were evaluated.
[0050]
(I) Perforation sensitivity
○: Predetermined drilling is performed reliably and good.
Δ: There are places where predetermined perforations cannot be obtained partially, but there is no practical problem.
X: There are many places where a predetermined perforation cannot be obtained, and there is a problem in practical use.
[0051]
(Ii) Independent perforation
○: Each dot is perforated independently.
Δ: Perforated almost independently, no problem in practical use.
X: The dots adjacent to each other are connected, and there is a practical problem.
In addition, printing was performed using a lithographic AP7200 printing machine manufactured by Riso Kagaku Kogyo Co., Ltd. using a stencil sheet, and the following characteristics of the obtained characters and images were visually determined.
[0052]
(Iii) Character printability
(1) Check for missing characters
(2) Presence or absence of uneven thickness of characters
Those markedly unusable in terms of (1) and (2) are marked with x, those with no problems at all are marked with ○, and those that are missing but uneven in thickness are marked with Δ. .
[0053]
(Iv) Evaluation of solid printability
● Using a base paper with a diameter of 0.5, 1.0, 3.0, 10.0, and 30.0 mmφ (round and filled with black inside) It was evaluated in the same way.
(1) Compatibility with solid paper size for solid printing
(2) Evaluation of shading unevenness in solid printing
In (1) and (2), those that are clearly unusable are indicated by X, those that are completely satisfactory are indicated by ○, and those that are problematic but usable are indicated by Δ.
[0054]
【Example】
Example 1
Polymerization was carried out in a conventional manner using dimethyl terephthalate / dimethyl isophthalate (molar ratio: 83/17) as the dicarboxylic acid component, and ethylene glycol as the glycol component, and 0.6 ppm of calcium carbonate particles having an average particle size of 1.2 μm were added thereto. 0.04% by weight of silica particles having a weight percent of 1.5 μm and an average particle size of 1.5 μm was added to obtain a copolyester having an intrinsic viscosity of 0.7.
[0055]
This polymer was extruded into a sheet at 275 ° C., and cooled and solidified on a rotating cooling drum set at 25 ° C. using an electrostatic application method. Then, the film was stretched 4.6 times in the machine direction at 105 ° C and 4.7 times in the transverse direction, and further heat treated at 120 ° C for 5 seconds and 90 ° C for 2 seconds, and a biaxially stretched film having a thickness of 1.7 µm. Manufactured.
[0056]
Example 2
Polymerization was carried out by a conventional method using dimethyl terephthalate / dimethyl isophthalate (molar ratio: 90/10) as the dicarboxylic acid component and ethylene glycol as the glycol component, and 1.2 wt. % To obtain a copolyester (polymer A) having an intrinsic viscosity of 0.75. 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 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. Next, the film was stretched 3.7 times in the machine direction at a temperature of 70 ° C., 80 degrees in the transverse direction and 4.0 times, followed by stretching at 100 ° C. and 1.2 times, and after heat treatment at 90 ° C. for 5 seconds, the thickness 1 A biaxially stretched film of 5 μm was produced. The obtained film was aged at 48 ° C. for 15 hours in a roll state.
[0057]
Example 3
Polymerization was carried out in a conventional manner using 2,6-naphthalenedimethyl / dimethyl isophthalate (molar ratio: 85/15) as the dicarboxylic acid component and ethylene glycol as the glycol component, and 1 silica particle having an average particle size of 1.2 μm was added to this. .2% by weight was added to obtain a copolyester (polymer A) having an intrinsic viscosity of 0.65. 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 were uniformly blended, extruded into a sheet at 280 ° C., and cooled and solidified on a rotating cooling drum set at 30 ° C. using an electrostatic application method. Next, the film was stretched by 80.degree. C. in the longitudinal direction at 3.7.times., 950.degree. C. and 4.0.times. In the transverse direction, followed by stretching at 100.degree. C. and 1.2.times. A biaxially stretched film of 7 μm was produced. The obtained film was aged at 48 ° C. for 15 hours in a roll state.
[0058]
Comparative Example 1
Polymerization was carried out in a conventional manner using dimethyl terephthalate / dimethyl isophthalate (molar ratio: 80/20) as the dicarboxylic acid component and ethylene glycol as the glycol component, and 0.5 weight of silica particles having an average particle diameter of 1.5 μm was added thereto. % To obtain a copolyester having an intrinsic viscosity of 0.7.
This polymer was extruded into a sheet at 275 ° C., and cooled and solidified on a rotating cooling drum set at 25 ° C. using an electrostatic application method. Subsequently, the film was stretched 4.2 times in the longitudinal direction at 105 ° C. and 3.8 times in the transverse direction, and further subjected to heat treatment at 140 ° C. for 5 seconds to produce a biaxially stretched film having a thickness of 2.0 μm.
[0059]
[Table 1]

[0060]
As can be seen from Table 1, the film according to the present invention was excellent in independent perforation, character printability, and solid printability, and had a high sensitivity that could sufficiently provide perforation sensitivity to practical use.
[0061]
【The invention's effect】
As described above, according to the highly sensitive thermosensitive stencil sheet paper of the present invention, independent perforation is good, both character printing and solid printing are clear and have high gradation, no printing unevenness, and plate making time. Thus, it is possible to stably provide a high-sensitivity heat-sensitive stencil sheet that can be printed with a higher dot density.

Claims (6)

A biaxially stretched polyester film having a thickness of 0.5 to 4 μm, wherein the three-dimensional surface center plane average roughness SRa [nm] of the film surface is 20 <SRa <40, and the film satisfies the following formula: High sensitivity heat sensitive stencil film for base paper.
[S (Tmax) −Y (Tmax)] + [S (Tmax + 30) −Y (Tmax + 30)] + [S (Tmax + 60) −Y (Tmax + 60)] ≧ 160 (1)
Tm-Tmax> 60 [° C.] Formula (2)
Tmax [° C.]: temperature indicating the maximum value of heat shrinkage stress of the film
Tm [° C.]: Melting point of film. However, if there are multiple melting points, the melting point on the lowest temperature side. S (T) [g / mm ² ]: heat shrinkage stress at temperature T [° C.] Y (T) [kg / mm ² ]: tensile elastic modulus of the film at temperature T [° C.]   The polyester film for a high-sensitivity heat-sensitive stencil sheet according to claim 1, wherein 300 <S (Tmax) <2000.   The polyester film for high-sensitivity heat-sensitive stencil printing paper according to claim 1 or 2, wherein S (Tmax) -Y (Tmax)> 0. The high-sensitivity heat-sensitive stencil polyester film according to any one of claims 1 to 3, wherein the lowest melting point of the film is <230 ° C. The polyester film for high-sensitivity heat-sensitive stencil printing paper according to any one of claims 1 to 4 , wherein the polyester film has a heat shrinkage rate of 65% at 65 ° C in the longitudinal direction. The polyester film for a high-sensitivity heat-sensitive stencil sheet according to any one of claims 1 to 5 , wherein the biaxially stretched polyester film is produced by simultaneous biaxial stretching.