JP2000094853A - Polyester film for heat-sensitive stencil printing base paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a polyester film for a heat-sensitive stencil printing base paper for processing and printing provided with sharpness and free from uneven thickness and uneven shade. SOLUTION: A biaxially oriented film is composed of polyester containing trimethylene terephthalate units, and the thickness of the film is 2 μm or more to 10 μm or less and the melting peak or peaks (including shoulder) observed by the DSC temperature rise measurement satisfy the condition a) two melting peaks or more exist in the range of 90 deg.C or higher to 250 deg.C or lower or the condition b) one melting peak exists in the range of 160 deg.C or higher to 240 deg.C or lower.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester film for heat-sensitive stencil printing base paper, and more particularly, to a polyester film containing polytrimethylene terephthalate as a polyester resin composition having high printing sensitivity, unevenness in the thickness of printed characters and figures, and the like.
The present invention relates to a polyester film for heat-sensitive stencil printing paper which has no density unevenness and enables clear plate making and printing.

[0002]

2. Description of the Related Art In recent years, heat-sensitive stencil printing using a stencil made by perforating plate by receiving heat from a xenon flash lamp, a thermal head, or a pulse irradiation of a laser beam or the like has attracted attention. The principle of this plate making method is described in, for example, Japanese Patent Publication No. 41-7623,
No. 103957, JP-A-59-143679, and the like.

Heretofore, as a base paper used for such heat-sensitive stencil printing, a heat-sensitive stencil printing paper film laminated with a porous support by an adhesive or heat has been used.
This heat-sensitive stencil film is made of vinyl chloride,
Vinylidene chloride copolymer films, polypropylene films, highly crystallized polyethylene terephthalate films have been used, and thin paper or polyester gauze has been used as a porous support. However, they have the following disadvantages. (1) When a vinyl chloride or vinylidene chloride copolymer film is used, printed characters are not clearly displayed. (2) With a polypropylene or polyethylene terephthalate film, clear characters can be obtained, but solid printing (a black mark or a black square such as a sign or a figure with a large ink adhesion area cannot obtain a clear one). (3) Shading appears on the printed portion in character printing or solid printing (4) Character thickness unevenness occurs partially (5) Sensitivity is poor, and black light text is not produced. To solve the drawbacks, see Japanese Patent Application Laid-Open No. 62-149496.
Japanese Patent Application Laid-Open No. 62-282983 discloses the use of a film having a small crystal melting energy, while Japanese Patent Application Laid-Open No. 62-282983 discloses a high heat shrinkage (100 ° C. × 10) made of a substantially amorphous thermoplastic resin.
The use of a film has been proposed.

[0004] However, the former has problems in production such as blocking during drying of polymer chips during the process of producing a film, and adhesion of a film edge after longitudinal stretching to a clip of a tenter type transverse stretching machine. ,
In addition, the polymer softened during perforation tends to adhere to the thermal head, and there is a problem in printing quality such as generation of streak-like white spots caused by polymer adherence during continuous plate making.

[0005] In the latter case, when excessive thermal energy is applied more than necessary for perforation, the hole tends to be excessively enlarged, and when printing with a high density of perforated dots such as solid printing, Since the residual polymer deformed by the thermal perforation around the perforated hole is clogged with the eyes of the porous support, there is a problem that white spots occur at places where black printing is to be performed, and the print density is reduced.

Further, there is a problem in the production of a stencil master such that a film shrinks due to a solvent when a film surface is coated with an anti-sticking coating or when a porous support and a film are laminated with an adhesive.

In order to solve these problems, for example, Japanese Unexamined Patent Publication No. 3-39294 proposes a film showing two or more melting peaks in a DSC temperature rise measurement, which has been put to practical use. In some hardware devices, the sensitivity as a heat-sensitive stencil sheet may be insufficient.
If the film is designed to have a large heat shrinkage ratio by using a polymer having a relatively low melting point in order to improve sensitivity, curling or wrinkling occurs due to high temperature (about 60 ° C. or higher) during storage or transportation. In some cases, the problem of "reduced property" may occur.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to eliminate the above-mentioned drawbacks, to provide clear printing for both printing and solid printing, to have no unevenness in the thickness of the printing, and to have no durable unevenness. An object of the present invention is to provide a film for heat-sensitive stencil printing base paper which is excellent in stability, has no wrinkles, has high sensitivity, and has excellent storage stability.

[0009]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that the aforementioned problems can be solved by using polytrimethylene terephthalate (hereinafter sometimes abbreviated as PTT) in a thermoplastic polyester resin. And arrived at the present invention.

That is, the present invention relates to a biaxially stretched film comprising a polyester containing trimethylene terephthalate units, wherein the film has a thickness of 0.2 μm or more and 10 μm or less, and has a melting peak (shoulder The following conditions a) or b) a) two or more in the range of 90 ° C or more and 250 ° C or less b) one or more in the range of 160 ° C or more and 240 ° C or less It is a polyester film for printing base paper.

Hereinafter, the present invention will be described in detail.

(Thermosensitive stencil sheet) As described above, the thermosensitive stencil sheet used in the present invention is a stencil sheet subjected to perforation by receiving heat from a xenon flash lamp, a thermal head, a laser beam, or the like. It is obtained by bonding a porous support to a film for use. Then, the film for heat-sensitive stencil printing base paper (hereinafter referred to as
The heat-sensitive film may form a portion in which characters and the like of the base paper to be printed are perforated when subjected to flash irradiation or contact with a thermal head.

The process of perforating the heat-sensitive film can be divided into the following three steps. (1) A portion to which thermal energy is applied is softened and melted by contact with a thermal head or irradiation of an electromagnetic wave (xenon flash lamp light, laser pulse, or the like), so that the holes can be tight. (2) Thermal energy is applied, and the polymer around the softened pore is thermally contracted / flowed by the diffused thermal energy to expand the pore. (3) The softened polymer is drawn to the periphery of the hole by the heat shrinkage force, solidifies by natural cooling and heat radiation, and the shape of the hole is maintained by forming the hole end. The heat-sensitive film of the present invention, in the temperature rise measurement of DSC,
Having one or more melting peaks at 90 ° C. or higher and 250 ° C. or lower, having a melting peak in a low temperature region compared to polyethylene terephthalate, making it easier to trigger pores, and including polytrimethylene terephthalate, It is characterized in that sufficient sensitivity and mechanical strength can be obtained as a heat-sensitive film.

(Polyester) The polyester used in the present invention contains terephthalic acid as a main acid component,
-A polyester containing trimethylene terephthalate units having propanediol as a main glycol component.

The polyester containing trimethylene terephthalate units has at least 55 of all repeating units.
A composition comprising a polyester in which mol% is a trimethylene terephthalate unit and another polyester is preferred.

It is preferable that at least 55 mol% of all the repeating units be a polyester copolymer having trimethylene terephthalate units.

(Composition) The composition used in the present invention comprises a polyester in which at least 55 mol% of all repeating units are trimethylene terephthalate units, and another polyester.

Polyesters in which at least 55 mol% of all repeating units are trimethylene terephthalate units include homopolymers having trimethylene terephthalate as all repeating units or 55 mol% or more of all repeating units.
Preferably, a copolymer (copolymer) in which at least 60 mol% is trimethylene terephthalate is used. When using a homopolymer of polytrimethylene terephthalate, it is preferable to use a composition with another polyester.

The proportion of the polyester in which at least 55 mol% of the total repeating units are trimethylene terephthalate units is at least 40% by weight, preferably 40 to 40% by weight.
It is 95% by weight, more preferably 40 to 70% by weight.

Other polyesters include polyethylene terephthalate, polyethylene isophthalate, polybutylene terephthalate, polytetramethylene tere (iso)
Terephthalate, polyethylene-4,4'-tetramethylenediphenyldicarboxylate, polyethylene-
2,6-naphthalenedicarboxylate, polyethylene-2,7-naphthalenedicarboxylate, polytrimethylene-2,6-naphthalenedicarboxylate, polybutylene-2,6-naphthalenedicarboxylate, polycyclohexanedimethylene terephthalate, Polyneopentylene-2,6-naphthalenedicarboxylate,
Poly (bis (4-ethyleneoxyphenyl) sulfone)
-2,6-naphthalenedicarboxylate and the like, among which polyethylene isophthalate,
Polyethylene terephthalate, polybutylene terephthalate, polyhexamethylene tere (iso) phthalate, polyethylene-2,6-naphthalenedicarboxylate,
Polytrimethylene-2,6-naphthalenedicarboxylate, polybutylene-2,6-naphthalenedicarboxylate, and poly (bis (4-ethyleneoxyphenyl) sulfone) -2,6-naphthalenedicarboxylate are preferred.

These other polyesters may be used alone or in combination of two or more kinds in the composition at 60% by weight or less, preferably 5 to 60% by weight, more preferably 30 to 60% by weight.
% By weight can be used. If the mixing amount of the mixture exceeds the above range, characteristics such as sensitivity, durability, and storability as heat-sensitive stencil printing base paper are unpreferably deteriorated. The production of such a composition can be carried out by a generally known method for producing a polyester composition.

In the present invention, a copolymer in which at least 55 mol% of all the repeating units are trimethylene terephthalate units can be used. In the copolymer (copolymer), as a copolymer component constituting a copolymer other than trimethylene terephthalate as a main component,
A compound having two ester-forming functional groups in the molecule can be used.

Such compounds include, for example, oxalic acid, adipic acid, phthalic acid, sebacic acid, malonic acid, succinic acid, glutaric acid, dodecanedicarboxylic acid, isophthalic acid,
4-cyclohexanedicarboxylic acid, 4,4′-diphenyldicarboxylic acid, 4,4′-diphenylsulfonedicarboxylic acid, 4,4′-diphenoxyethanedicarboxylic acid,
Phenylindanedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 1,5-
Dicarboxylic acids such as naphthalenedicarboxylic acid, tetralindicarboxylic acid, decalindicarboxylic acid, diphenyletherdicarboxylic acid, etc .; oxycarboxylic acids such as p-oxybenzoic acid, p-oxyethoxybenzoic acid, etc .; or ethylene glycol, tetramethylene glycol, pentamethylene Glycol, hexamethylene glycol, cyclohexane methylene glycol, neopentyl glycol, ethylene oxide adduct of bisphenolsulfone, ethylene oxide adduct of bisphenol A,
Dihydric alcohols such as diethylene glycol, polyethylene oxide glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol and the like can be preferably used. The proportion of the copolymer component is preferably 5 to 30 mol%.

These copolymer components are not only one kind but also two.
More than one species can be used simultaneously. Of these, isophthalic acid, 4,4'-diphenyldicarboxylic acid, 2,6-naphthalenedicarboxylic acid, p-oxybenzoic acid are preferred as the acid component, and ethylene glycol, tetramethylene glycol, pentamethylene is preferred as the glycol component. It is an ethylene oxide adduct of glycol, hexamethylene glycol, neopentyl glycol, and bisphenolsulfone.

The polytrimethylene terephthalate may be one in which a terminal hydroxyl group and / or a carboxyl group is partially or entirely blocked by a monofunctional compound such as benzoic acid or methoxypolyalkylene glycol. A very small amount of a trifunctional or higher functional ester-forming compound such as glycerin or pentaerythritol may be copolymerized within a range where a substantially linear polymer can be obtained.

The polyester in the present invention is a conventionally known method, for example, a method of directly obtaining a low-polymerized polyester by a reaction of dicarboxylic acid and glycol, or a conventionally known transesterification catalyst for converting a lower alkyl ester of dicarboxylic acid and glycol. For example, after reacting with one or more compounds containing sodium, potassium, magnesium, calcium, zinc, strontium, titanium, zirconium, manganese, and cobalt, polymerization is carried out in the presence of a polymerization catalyst.

Examples of the polymerization catalyst include antimony compounds such as antimony trioxide and antimony pentoxide, germanium compounds typified by germanium dioxide, tetraethyl titanate, tetrapropyl titanate, tetraphenyl titanate or partial hydrolysates thereof, and oxalic acid. Examples include titanium compounds such as titanyl ammonium, potassium titanyl oxalate, and titanium trisacetylacetonate.

The polyester may be formed into chips after melt polymerization and solid-phase polymerized under reduced pressure under heating or in an inert gas stream such as nitrogen.

(Additives) The biaxially stretched film of the present invention is used for improving transportability, windability, coating at the time of preparing base paper, laminating process and workability at the time of printing, or thermal head at the time of hot perforation. In order to prevent fusion of the film and the film, it is preferable that the surface is roughened to give an appropriate lubricity. As for the degree of the surface roughening, the center line average roughness (Ra) is 5 to 500 nm, and more preferably 10 to 47 nm.
It is preferably 0 nm, particularly preferably 15 to 450 nm.

As the surface roughening agent, fine particles having an average particle size of 0.05 to 5.0 μm are contained in the film in an amount of 0.001 to 5.0.
% By weight, preferably 0.004 to 3.0% by weight. The fine particles may be internally precipitated particles or externally added particles.

Examples of the externally added particles include calcium carbonate, magnesium carbonate, barium carbonate, barium sulfate, calcium phosphate, lithium phosphate, magnesium phosphate, lithium fluoride, aluminum oxide, silicon oxide (silica), titanium oxide, kaolin, Talc, carbon black, silicon nitride, boron nitride, crosslinked polymer fine particles (for example, crosslinked polystyrene, crosslinked acrylic resin,
Fine particles such as a crosslinked silicone resin). These may be used alone or in combination of two or more. Among them, those having a sharp particle size distribution and spherical particles are preferable, and spherical silica particles are particularly preferable. Here, the term “spherical” means that the ratio of major axis / minor axis is 1.0 to 1.2.
Means

As a method for incorporating such a surface roughening agent, there are internal particle precipitation method in which an alkali (earth) metal compound is precipitated as fine particles by adding a phosphating compound during production of polyester or the like, An external particle addition method in which an inorganic or organic fine particle inert to a polymer is added in any of the film forming steps.

The polyester film of the present invention comprises a pigment,
UV absorbers, release agents, lubricants, flame retardants, antistatic agents,
Polysiloxane and the like can be blended.

The timing of adding the inert fine particles and other additives is not particularly limited as long as it is a stage before the polyester film is formed. For example, it may be added at the polymerization stage. You may.

(Porous Support) The porous support to be bonded to the heat-sensitive film of the present invention is not particularly limited, and typical examples thereof include Japanese paper, tentacles, synthetic fiber paper, various woven fabrics, and nonwoven fabrics. It can be mentioned as. The basis weight of the porous support to be used is not particularly limited, but is usually ^{2 to 20} g / m ² , preferably about 5 to 15 g / m ² . When a mesh sheet is used, it is preferable to use a woven fiber having a thickness of 20 to 60 μm, and it is preferable to use one having a lattice spacing of 20 to 250 μm.

The adhesive used for bonding the heat-sensitive film of the present invention to the porous support is not particularly limited, but examples thereof include vinyl acetate resins, acrylic resins, urethane resins and polyester resins. Examples can be given.

(Film Thickness) The thickness of the polyester film of the present invention is from 0.2 μm to 10 μm, preferably from 0.4 μm to 8 μm, particularly preferably from 0.6 μm to 5 μm. This thickness is 0.2μ
When the molecular weight is less than m, it is difficult to bond with a porous support, the printed image is unclear, and shading tends to occur, and the printing durability also decreases. On the other hand, when the thickness is more than 10 μm, the perforation sensitivity is low, resulting in a missing portion or uneven thickness of the printed image, which is not preferable.

(Melting Peak Temperature) In the polyester film of the present invention, the melting peak (including the shoulder) observed in the DSC temperature rise measurement must satisfy the following conditions a) or b). a) two or more in the range of 90 ° C or more and 250 ° C or less b) one or more melting peaks (including shoulders) in the range of 160 ° C or more and 240 ° C or less On the other hand, if there is only one melting peak, if it is outside the above range (condition b), the printing base paper will have poor sensitivity. When the melting peak (including the shoulder) temperature is lower than 90 ° C., it is difficult to form a film. It is preferable that two or more melting peaks (including shoulders) are observed. In this case, the melting point Tm on the highest temperature side
p (max) and melting point Tmp (mim) at the lowest temperature
, That is, [Tmp (max) + Tmp (mi
m)] / 2 is 190 ° C. or higher, more preferably 200 ° C.
Above, particularly preferably at least 205 ° C.,
The temperature is preferably 5 ° C or lower, more preferably 230 ° C or lower.

(Young's Modulus) The polyester film of the present invention preferably has a Young's modulus of 110 kg / mm ² or more and 600 kg / mm ² or less in both the machine direction (MD) and the transverse direction (TD). Preferably 150 kg / mm ² or more 60
0 kg / mm ² or less, particularly preferably 180 kg / mm ²
It is at least 550 kg / mm ² . 110 kg / mm ²
If the stencil paper is used, the workability and printing durability when stencil paper is used are insufficient. If it exceeds 600 kg / mm ² , it becomes difficult to form a film, and productivity is remarkably reduced.

(Surface Roughness Ra) The surface roughness Ra of the polyester film of the present invention is preferably 5 nm or more and 500 nm or less. More preferably 10 nm or more and 47
0 nm or less, particularly preferably 15 nm or more and 450
nm or less. If the surface roughness Ra is less than 5 nm, blocking is likely to occur when the films overlap,
Handling properties deteriorate. On the other hand, when the thickness exceeds 500 nm, the end face is easily shifted in handling after winding the film in a roll shape.

(Thickness unevenness) The thickness unevenness of the film of the present invention is 1
It is preferably at most 2%. More preferably, 10
%, Particularly preferably 8% or less. 12 thick spots
%, Perforation spots are generated, causing print shading and sensitivity reduction.

The heat shrinkage of the film at 150 ° C. for 30 minutes is preferably 10% or more, more preferably 15% or more, in both the machine direction (MD) and the transverse direction (TD). If it is less than 10%, the perforation diameter does not increase and the sensitivity is low.

Further, it is preferable that each of the longitudinal heat shrinkage (S _MD ) and the transverse heat shrinkage ( _STD ) at 60 ° C. for 120 minutes is 2% or less. If it exceeds 2%, when the heat-sensitive stencil sheet as a product is exposed to a temperature of about 60 ° C. or more during transportation or storage, the film shrinks, and wrinkles and curls may be generated on the base paper. . Base paper that is liable to cause such a phenomenon has poor storage stability and has low product value. A method for reducing the heat shrinkage in the vertical and horizontal directions at 60 ° C. for 120 minutes to 2% or less is not specified.
50 to 5 film rolls before processing into heat-sensitive stencil paper
A method of supporting the core in a thermostat at 5 ° C. and storing it for 3 days or more is suitably used.

The intrinsic viscosity (IV) obtained by dissolving the film in orthochlorophenol and using an Ostwald viscometer is preferably from 0.45 dl / g to 0.90 dl / g.

(Specific production conditions) The polyester film of the present invention is a biaxially stretched film made of polyester containing polytrimethylene terephthalate as a component of the polyester composition. The biaxially stretched film is melted at a melting point or higher by a usual method, extruded onto a casting drum cooled from a die slit and solidified by cooling to obtain an unstretched polyester film. The unstretched film can be manufactured by biaxially stretching it in the longitudinal and transverse directions and then heat-setting.

The film is stretched by a known roll-type longitudinal stretching machine, infrared heating longitudinal stretching machine, tenter clip type transverse stretching machine, a multi-stage stretching machine which performs these stretching in a plurality of stages, a tubular stretching machine, and an oven-type vertical stretching machine. The stretching can be performed using a stretching machine, a simultaneous biaxial tenter stretching machine, or the like, but is not particularly limited.

Next, the method for producing the polyester film of the present invention will be described in detail, but is not necessarily limited thereto. As described above, the unstretched polyester film obtained by a known method is stretched 2 to 5 times in the machine direction at 40 to 130 ° C. using an infrared heating type longitudinal stretching machine. A roll heating type vertical stretching machine may be used, but an infrared heating type is preferable because defects such as scratches are easily generated on the film surface.

After the longitudinal stretching, the film is further subjected to 40-13 in a stenter.
Stretched 2 to 5 times in the transverse direction at 0 ° C, and 1 to 60 to 235 ° C.
By performing heat treatment for 100 seconds, a desired polyester film can be obtained. When the heat treatment temperature exceeds 235 ° C., rupture frequently occurs at the time of film formation, and the film forming property is extremely deteriorated. When it is desired to reduce the heat shrinkage in the transverse direction, 1 to 15% relaxation in the width direction can be given during the heat treatment. Further, multi-stage stretching in which the above-described stretching in the longitudinal direction and / or the transverse direction is divided into a plurality of stages may be used.
In particular, longitudinal multi-stage stretching is preferable because uneven thickness can be suppressed. The polyester film of the present invention may be laminated with another film by a co-extrusion method or an extrusion laminating method during the film forming step, or may be laminated with an adhesive after forming the film.

As described above, the roll obtained by slitting the polyester film of the present invention into a product width and winding it is aged under appropriate conditions (for example, 50 ° C. for 3 days) to improve the preservability of the heat-sensitive film product, curl, Wrinkles can be prevented.

[0050]

The present invention will be further described with reference to the following examples.
The present invention is not limited only to the following examples unless the gist is changed. The measurement methods and definitions of various physical property values and characteristics in the present invention are as follows.

(1) Calculation of Component Amounts (Mole Ratio of Main Component, Copolymer Component) of Trimethylene Terephthalate A film sample was measured with a solvent (CDCl ₃ : CF ₃ COO).
(D = 1: 1), and ¹ H-NMR measurement is carried out, and it is calculated by the integration ratio of each obtained signal.

(2) Melting peak temperature 10 mg of the film was added to TA Instruments Th.
thermoAnalyst 2100, heated in a nitrogen stream at a heating rate of 20 ° C./min, and analyzed the endothermic behavior of the film due to melting by the first and second derivatives, and determined the temperature at which a peak or shoulder occurred. Was determined and this was taken as the melting peak temperature.

(3) Film thickness (t) The thickness t (μm) of the film is expressed by W (c)
m), when the length was sampled to L (cm), the weight was G (g), and when the density was d (g / cm ³ ), it was calculated by the following equation.

[0054]

## EQU1 ## t = 10000G / (W.L.d)

(4) Surface Roughness (Center Line Surface Roughness Ra) Both the front and back sides of the film are measured with a surface roughness meter (Surfcom 111A, Tokyo Seimitsu Co., Ltd.), and the average value is calculated to obtain the surface roughness.

(5) Young's modulus The film was cut into a specimen having a width of 10 mm and a length of 15 cm, and the distance between the chucks was set to 100 mm, and the film was pulled at a tensile speed of 10 mm / min and a chart speed of 500 mm / min by an Instron type universal tensile tester. The Young's modulus (kg / mm ² ) was calculated from the tangent at the rising portion of the obtained load-elongation curve.

(6) Thickness unevenness Optical interference film thickness meter (MCPD-2000) manufactured by Otsuka Electronics Co., Ltd.
Is measured over a length of 2 m in each of the longitudinal direction and the lateral direction of the film to obtain a continuous thickness chart. Read the maximum thickness and minimum thickness from this chart.

Further, for the same sample, the width (c
m), length (cm), weight (g), density (g / cm ³ )
From above, the thickness (μm) is calculated by the above-mentioned formula, and the average thickness is obtained.

The ratio of the difference between the above-mentioned maximum thickness and minimum thickness to the average thickness was calculated by the following equation, and was determined as thickness unevenness.

[0060]

## EQU2 ## Thickness unevenness (%) = {(maximum thickness−minimum thickness) / average thickness} × 100

(7) Evaluation of character printing (7-1) Evaluation of clarity of bunko A JIS first-level character was used as a manuscript having a character size of 3.0 mm □, and a porous support made of polyester gauze was used. A heat-sensitive film (the same is applied to the examples and comparative examples) is bonded to a “RISO business card game” as a flash irradiation method.
Using a plate making / printing machine (manufactured by Riso Kagaku Co., Ltd.)
Plates made and printed using "ORT SS950 (manufactured by Ricoh Co., Ltd.)" were visually observed and evaluated according to the following criteria. In addition, the final evaluation showed the worse evaluation result of the flash irradiation perforation method and the thermal head perforation method in each of Examples and Comparative Examples. A: What looks the same as the manuscript B: Unlike the manuscript, the lines are partially cut or stuck, but can be read C: Those that are cut or stuck to a state where they can hardly be read

(7-2) Evaluation of Missing Characters The same plate making and printing as in (7-1) were performed, and the manner of missing characters was evaluated according to the following criteria. ：: no missing △: not completely missing, but slight (to the extent readable) missing ×: clearly missing and unusable

(7-3) Evaluation of Unevenness of Character Thickness A character having a character size of 4.0 mm □ was printed using the same plate making and printing machine as in (7-1), and the printed state was visually observed. Evaluation was made according to the following criteria. ：: Good appearance with no unevenness of thickness and usable ×: Clearly uneven thickness of characters compared to the original manuscript,
Things that can't be used because they look bad

(7-4) Evaluation of Thickness of Buns: Plate making and printing were performed in the same manner as in (7-3), and changes in the thickness of characters were visually observed and evaluated according to the following criteria. ：: Thickness unchanged Δ: Slightly thicker or thinner but usable ones ×: Compared with the text thickness of the original, clearly thicker or thinner Things that cannot be used

(8) Evaluation of Solid Printing (8-1) Evaluation of Clearness of Solid Printing Using a black circle of 1 to 5 mmφ (circled and black inside) as an original, The same plate making and printing as in the above) were evaluated according to the following criteria. Based on the size of the document as a reference, judgment was made based on the partial irregularities of the outline. ○: Irregularities of 70 μm or less and clear; Δ: Intermediate between ○ and ×, usable depending on the method ×: Irregularities of 250μm or more in size from the size of the original, poor appearance and unclear

(8-2) Correspondence with Original Size for Solid Printing Printing is performed in the same manner as in (8-1), and printing is performed in all directions (0 ° and 180 °,
45 ° and 225 °, 90 ° and 270 °, 135 ° and 31
(At a position of 5 °) was measured, and the absolute value of the difference from the size of the document was obtained and evaluated according to the following criteria. ：: 70 μm or less Δ: More than 70 μm and less than 550 μm (available depending on the application) ×: 550 μm or more

(8-3) Evaluation of solid printing shading The printing was performed in the same manner as in (8-1), and the presence or absence of solid printing shading was visually observed and evaluated according to the following criteria. ：: No unevenness ×: Unevenness

(9) Evaluation of sensitivity Five types of pencil hardness of 5H, 4H, 3H, 2H and H were prepared, and a document was written with a pressing force of 170 g as a manuscript. The evaluation was made based on the pencil hardness, which is the highest hardness that can be read. Those that can read the lightest characters written in 5H have the highest sensitivity, and those that can read only the characters written with darker pencils are determined to have lower sensitivity.

(10) Evaluation of Durability The number of sheets that can be printed by the above-described printing machine before the heat-sensitive film was damaged (hereinafter, referred to as printing durability).

(11) Evaluation of wrinkles The sample was divided into two parts, one was bonded to a polyester gauze by the usual method, and the other was slit to a width narrow enough to take an A4 size plate, and both ends were widened. It was carefully bonded with polyester gauze to minimize wrinkles by nipping with a roller. The two sensitivities were compared and evaluated according to the following criteria. ：: No difference ：: Difference is 1H or less Δ: Difference is 2H ×: Difference is 3H or more

(12) Evaluation of Storage Stability The laminated base paper was left in a gear oven at 65 ° C. for 24 hours, and then visually evaluated for wrinkles and curls, and judged according to the following criteria. ：: No practically harmful change occurred before and after leaving ×: Practical harmful change occurred before and after leaving

Examples 1 to 9 and Comparative Examples 1 to 12 The following polymers were mixed and used as thermoplastic polyester resin raw materials as shown in Table 1. In order to ensure slipperiness, each of the particles was made of spherical silica having an average particle size of 1.5 μm in an amount of 0.35% by weight.
Was added.

(A) Polytrimethylene terephthalate 100 parts by weight of dimethyl terephthalate, 60 parts by weight of 1,3-propanediol and 0.1 part of tetrabutyl titanate.
A transesterification reaction was performed using 08 parts by weight. Next, spherical silica particles having an average particle size of 1.5 μm were added as a lubricant so as to be 0.35% by weight per polymer, and a polycondensation reaction was carried out under a high vacuum to give an intrinsic viscosity of 0.65 dl / g.
Of polytrimethylene terephthalate (abbreviated as PTT) was obtained. (B) polyethylene terephthalate (intrinsic viscosity; 0.6
5, abbreviated as PET) (c) Polybutylene terephthalate (intrinsic viscosity; 1.1)
0, abbreviated as PBT) (d) Polyethylene-2,6-naphthalenedicarboxylate (intrinsic viscosity; 0.65, abbreviated as PEN) (e) 2,10,2,6-naphthalenedicarboxylic acid
Polyethylene terephthalate copolymer (intrinsic viscosity: 0.65,
PET / NDC5, PET / NDC10, PET / ND
(F20) PET / NDC25) (f) Polyethylene terephthalate copolymer in which isophthalic acid was copolymerized at a ratio of 10, 20, and 25 mol% (intrinsic viscosities: 0.65 and PET / I1, respectively)
0, abbreviated as PET / I20 and PET / I25) (g) Polyhexamethylene terephthalate copolymer in which isophthalic acid is copolymerized at a ratio of 10 mol% (intrinsic viscosity; 1.30, abbreviated as PHMT / I10) (H) Polybutylene terephthalate copolymer obtained by copolymerizing isophthalic acid at a ratio of 5 mol% (intrinsic viscosity; 1.)
(PBBT / I5) (i) polyhexamethylene terephthalate (intrinsic viscosity;
1.j PHMT) (j) Polytrimethylene terephthalate copolymer in which isophthalic acid is copolymerized at a ratio of 10, 20 mol% (intrinsic viscosity: 0.65, abbreviated as PTT / I10, PTT / I20)

After sufficiently drying the above raw materials, the raw materials are supplied to an extruder, and the temperature suitable for the used resin composition is set at 245 to 310 ° C.
, And the mixture was melt-extruded and cooled and solidified by a casting drum having a surface temperature of 20 ° C. by using an electrostatic application casting method to prepare an unstretched film. Note that Comparative Example 13 was extruded at a temperature 20 ° C. higher than the extrusion temperature of Example 1 and under the condition that the residence time in the extrusion system was five times.

The stretching temperature of this unstretched film is selected from the range of 50 to 130 ° C. suitable for the resin composition used, and is 3.2 to 4.0 times in the machine direction and 3.5 to 4.3 times in the transverse direction. After successive biaxial stretching at a magnification of 100, once cooled, then 100 to 15
Heat treatment was performed while relaxing at 0 ° C. by 2%. Before processing any of the samples into a heat-sensitive stencil sheet, the film roll was stored in a thermostat at 50 ° C. for 3 days while supporting the core.

The thus obtained biaxially stretched film having a thickness of 1.8 μm was bonded to a polyester gauze (made of polyethylene terephthalate fiber) and evaluated by a plate making / printing machine. The results are shown in Tables 2 and 3.

[0077]

[Table 1]

[0078]

[Table 2]

[0079]

[Table 3]

[0080]

The polyester film for heat-sensitive stencil paper of the present invention exhibits the following excellent functions and effects.

That is, the base paper using the film can be used for (1) clear plate making and printing in both of printing and solid printing. (2) Plate making and printing without unevenness of thickness and light and shade can be performed by printing with a bun and a solid printing. (3) The sensitivity is extremely high. (4) High sensitivity can be stably obtained without wrinkles. (5) Excellent storage stability. Features such as

Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat II (Reference) C08L 67:02 F term (Reference) 2H114 AB25 BA06 DA56 DA73 FA02 FA06 FA09 4F071 AA45 AA83 AA87 AF20Y AF54 AF57 AH12 BA01 BB06 BB08 BC01 BC10 BC12 BC16 4F210 AA24C AA24E AE01 AG01 QC06 QG01 QG18 QW12

Claims (6)

[Claims] 1. A biaxially stretched film comprising a polyester containing trimethylene terephthalate units, wherein the film has a thickness of 0.2 μm or more and 10 μm or less,
Two or more melting peaks (including shoulders) observed in the temperature rise measurement are present in the following conditions a) or b) a) in the range of 90 ° C or more and 250 ° C or less b) In the range of 160 ° C or more and 240 ° C or less A polyester film for heat-sensitive stencil printing paper, characterized by satisfying the following conditions. 2. The polyester containing trimethylene terephthalate units is a composition comprising a polyester in which at least 55 mol% of all repeating units are trimethylene terephthalate units and another polyester.
Polyester film according to 1. 3. The polyester film according to claim 1, wherein the polyester containing trimethylene terephthalate units is a polyester copolymer in which at least 55 mol% of all repeating units are trimethylene terephthalate units. 4. The film has a Young's modulus in the machine direction (MD),
110 kg / mm ² or more and 600 k in both transverse directions (TD)
g / mm < ² > or less, The polyester film in any one of Claims 1-3 characterized by the above-mentioned. 5. The film according to claim 1, wherein the film has a surface roughness (Ra) of 5 nm or more and 500 nm or less.
The polyester film according to any one of the above. 6. The polyester film according to claim 1, wherein the thickness unevenness of the film is 12% or less.