JP2002029170A - Film for heat sensitive stencil printing base paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a film for a heat sensitive stencil printing base paper, in which both the clear printing of a character and the clear solid printing are developed, neither ununiform printing thickness nor ununiform shading develops, wrinkle are hard to develop, durability and preservability are excellent and a printing sensitivity can be kept unvaried especially even in high speed printing. SOLUTION: This film is biaxially oriented polyester, film, which is made of a polyester composition including 40 wt.% or more of a polybutylene terephthalate copolymer having a thickness of 0.2 to 7.0 μm, a melting point (Tm) of 180 deg.C or higher and 230 deg.C or lower, a planar orientation coefficient (Ns) of 0.120 or more and 0.145 or less and the melt viscosity satisfying formula (1): 200<=V(Tm+20)-V(Tm+40)<=700, wherein V(Tm+20) represents a melt viscosity (poise) in shearing speed of 1,000 s-1 at a temperature, which is higher by 20 deg.C than the melting point of the film and V(Tm+40) represents a melt viscosity (poise) in shearing speed of 1,000 s-1 at a temperature, which is higher by 40 deg.C than the melting point of the film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film for heat-sensitive stencil printing paper, and more particularly to a film for heat-sensitive stencil printing paper having high printing sensitivity, clear printing, and excellent durability and storage stability.

[0002]

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

Conventionally, as a base paper used for such heat-sensitive stencil printing, a film obtained by laminating a film for a heat-sensitive stencil printing paper and a porous support with an adhesive or heat is used. 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. -When a vinyl chloride or vinylidene chloride copolymer film is used, printed characters are not clearly displayed. -With a polypropylene or polyethylene terephthalate film, clear characters can be obtained, but solid printing (symbols or figures with a large ink adhesion area) cannot obtain clear ones. -In any case, shades appear on the printed part. -Character thickness unevenness occurs partially.・ Sensitivity is poor, and black thin characters etc. do not appear. -When an amorphous polymer such as PET-G is used alone, the perforation diameter becomes too large and a large amount of ink is consumed. is there.

In order to solve these disadvantages, Japanese Patent Laid-Open No.
No. 149496 proposes the use of a film having a low crystal melting energy. However, during the film manufacturing process, there are manufacturing problems such as blocking during drying of the polymer chip, adhesion of the longitudinally stretched film edge to the clip of the tenter type transverse stretching machine, and the polymer softened at the time of perforating the thermal head. Easy to adhere,
During continuous plate making, there is a problem in print quality such as generation of streak-like white spots caused by polymer deposits. In order to solve these problems, for example, Japanese Patent No. 2507612 proposes a film showing two or more melting peaks in DSC temperature rise measurement, and it is being put to practical use. In some cases, the sensitivity as a heat-sensitive stencil sheet may be insufficient, and further improvement has been desired. In addition, wrinkles may easily occur as a heat-sensitive stencil sheet.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide clear printing of characters and solid printing, no unevenness in printing thickness, no uneven shading, and no wrinkles. It is an object of the present invention to provide a film for heat-sensitive stencil printing base paper which is difficult to perform, has excellent durability and storability, and can maintain printing sensitivity even at high speed printing.

[0006]

That is, the present invention provides a biaxially stretched polyester film having a thickness of 0.2 to 7.0 μm, wherein the film contains a polybutylene terephthalate copolymer in an amount of 40% by weight or more. And the melting point (Tm) of the film is 180 ° C. or higher and 230 ° C.
Hereinafter, the plane orientation coefficient (Ns) is 0.120 or more and 0.145 or more.
A heat-sensitive stencil film for stencil printing, characterized in that the melt viscosity satisfies the range of the following formula (1). 200 ≦ V (Tm + 20) −V (Tm + 40) ≦ 700 (1) (In the above formula (1), V (Tm + 20) is the film melting point +
The melt viscosity (poise) at a shear rate of 1000 sec ^-1 at 20 (° C.) and V (Tm + 40) represent the melt viscosity (poise) at a shear rate of 1000 sec ^-1 at a film melting point of +40 (° C.). In the above structure, the polybutylene terephthalate copolymer preferably has a melting point of 180 ° C. or more and 220 ° C. or less.

The heat-sensitive stencil sheet in the present invention is, as described above, a sheet made by perforation by receiving heat from a xenon flash lamp, a thermal head, a laser beam, or the like. The support is laminated. The film for thermal printing base paper (hereinafter, sometimes simply referred to as a thermal film) is perforated when printing flash paper or contacting with a thermal head, such as characters and images of the printing base paper. The process of perforating the heat-sensitive film can be divided into the following three stages. (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 a hole can be triggered. (2) The thermal energy is applied, and the polymer around the softened pore is thermally contracted 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.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Polyester Composition For the film of the present invention, a polyester composition containing at least 40% by weight of a polybutylene terephthalate copolymer is used. When the ratio of the polybutylene terephthalate copolymer is 4
When the content is less than 0% by weight, gradation is poor and printing becomes unclear, and the printing sensitivity particularly during high-speed printing is undesirably reduced. This copolymer component may be an acid component or an alcohol component. Examples of the acid component include aromatic dicarboxylic acids such as isophthalic acid, phthalic acid, and naphthalenedicarboxylic acid, adipic acid, azelaic acid, sebacic acid, and decane dicarboxylic acid.Also, examples of the alcohol component include ethylene glycol and diethylene glycol. Examples thereof include aliphatic diols such as trimethylene glycol and hexanediol, and alicyclic diols such as cyclohexanedimethanol. These can be used alone or in combination of two or more. The proportion of the copolymer component depends on the type thereof, but is preferably a proportion that results in a polymer melting point in the range of 180 to 220 ° C. If the melting point of the polymer is less than 180 ° C., the crystallinity is poor, so that the tenter greatly adheres to the clip and a film cannot be formed. On the other hand, when the polymer melting point is 2
If the temperature exceeds 20 ° C., the melting point of the copolymer is too high, but the sensitivity at the time of high-speed printing decreases. Here, the melting point measurement of the copolymerized polyester is based on the melting point measurement method of the film.

The polyester composition used in the present invention contains not more than 60% by weight of a polyester other than the above-mentioned polybutylene terephthalate copolymer. Such a polyester is a thermoplastic polyester obtained by polycondensing an acid component and a glycol component. As the acid component, 2
Compounds having two ester-forming functional groups, such as phthalic acid, isophthalic acid, 5-sodium sulfoisophthalic acid, terephthalic acid, 2-potassium sulfoterephthalic acid,
2,6-naphthalenedicarboxylic acid, phenylindanedicarboxylic acid, diphenyletherdicarboxylic acid, oxalic acid, succinic acid, adipic acid, suberic acid, sebacic acid,
Dodecanedioic acid, eicosandioic acid, dimer acid,
Examples thereof include 1,4-cyclohexanedicarboxylic acid, decalindicarboxylic acid, hexahydroterephthalic acid, and ester-forming derivatives thereof. As the glycol component, ethylene glycol, propylene glycol,
1,2-propanediol, 1,3-butanediol,
1,4-butanediol, 1,5-pentanediol,
1,6-hexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol,
1,4-cyclohexanedimethanol, p-xylylene glycol, ethylene oxide adduct of bisphenol A, ethylene oxide adduct of bisphenol sulfone, triethylene glycol, polyethylene oxide glycol, polytetramethylene oxide glycol,
Neopentyl glycol and the like can be mentioned. Further, hydroxycarboxylic acids such as p-hydroxyethoxybenzoic acid and p-hydroxybenzoic acid and lower alkyl esters thereof can also be used.

The above-mentioned polyester may be one obtained by blocking a part or all of a terminal hydroxyl group and / or a carboxyl group with a monofunctional compound such as benzoic acid and methoxypolyalkylene glycol.
Alternatively, it may be modified with an extremely small amount of a trifunctional or higher functional ester-forming compound such as glycerin or pentaerythritol within a range where a substantially linear polymer can be obtained.

Among these, typical examples of the polyester include poly-2,6-naphthalenedicarboxylate and its copolymer, polyethylene terephthalate and its copolymer, and polyhexamethylene terephthalate copolymer. No. In the present invention, it is preferable to use at least one polyester selected from poly-2,6-naphthalenedicarboxylate and its copolymer, isophthalic acid copolymerized polyethylene terephthalate and polyhexamethylene terephthalate copolymer. The polyester may include a resin other than the polyester without departing from the spirit of the present invention.

Melting Point of Film The melting point of the film of the present invention must be 180 ° C. or higher and 230 ° C. or lower. If the film melting point is lower than 180 ° C., the polymer softened at the time of perforation easily adheres to the thermal head, and there is a problem in print quality such as generation of streak-like white spots due to polymer adherence during continuous plate making. Occurs. Further, an image without gradation is likely to be obtained. Moreover,
This is not preferable because the printing durability deteriorates. On the other hand, if the film melting point exceeds 230 ° C., the perforation sensitivity is lowered, which is not preferable.

Since the film of the present invention comprises a polyester composition comprising two or more polyesters,
In some cases, two or more melting points of the film are measured. In that case, the highest melting point is defined as the melting point of the film.
That is, in the present invention, it is sufficient that the highest melting point of the film satisfies the above melting point range.

The melting point of the film can be controlled within the range specified in the present invention by adjusting the type, copolymerization amount and blending ratio of each polyester constituting the polyester composition. The film temperature can also be adjusted by the melt extrusion temperature during film formation, the extruder residence time, and the like.

The polyester composition of the present invention may contain organic or inorganic particles in order to improve the slip property of the film. In the present invention,
If the average particle size of the added particles is large, breakage tends to occur during film formation. The average particle size of the added particles is 3 μm or less, further 2 μm
The following is preferred. Further, for example, it is preferable to add a spherical lubricant such as spherical silica particles, and one kind of the average particle diameter of the lubricant is about 1.5 ± 0.5 μm, and the other kind is 0.3 ± 0.3 μm.
It is even more preferable that the size is two types of about 0.2 μm.

The polyester composition may further contain an additive having an absorption peak in the wavelength range of flash light irradiation, and a lubricant and a surfactant may be added for the purpose of improving the releasability from the base paper. You may.

Method for Producing Film The film of the present invention is prepared by adding the above-mentioned additives to the above-mentioned polyester composition as required, drying the mixture sufficiently, supplying the extruder to a slit die (for example, a T-die). Alternatively, it is obtained by forming a melt film by an inflation casting method or the like and then biaxially stretching. The method of biaxial stretching is not particularly limited, but sequential biaxial stretching or simultaneous biaxial stretching (stenter method, tube method) can be used. The biaxially stretched film thus obtained may be appropriately subjected to a heat treatment. The heat treatment conditions are not particularly limited, but the heat treatment is usually performed at a temperature of 80 to 200 ° C. and a relaxation rate of 20% or less.

The film of the present invention may be one obtained by subjecting the film surface to a corona discharge treatment in air, carbon dioxide gas or nitrogen gas in order to improve the adhesion to the porous support.

Film Thickness In the present invention, the thickness of the biaxially stretched film is from 0.2 to
7.0 μm, preferably 0.5 μm.
To 5.0 μm, more preferably 0.8 to 3.5 μm. If the thickness is less than 0.2 μm, it will be difficult to bond with a porous support, and the printing will be unclear, and shading will easily occur, and the printing durability will also decrease. On the other hand, if the thickness exceeds 7.0 μm, the sensitivity is low, and the printing may have a missing portion or a thickness irregularity, which is not preferable.

Thermal Shrinkage of Film The heat shrinkage of the film of the present invention after heat treatment at 100 ° C. for 10 minutes has a longitudinal shrinkage (SMD) and a transverse shrinkage (STD).
D) Both are preferably 10 to 25%, more preferably 12 to 23%. If the heat shrinkage is less than 10%, the plate-making sensitivity of the film becomes poor, which may cause a practical problem.
Conversely, if it exceeds 25%, it becomes difficult to maintain the shape of the holes, and an excessive amount of ink is consumed, which is not preferable. In order to prevent wrinkles and curls from being generated or exposed due to unexpectedly high temperature (50 ° C. or more) during storage of the heat-sensitive stencil paper,
Heat shrinkage after heat treatment at 120 ° C for 2 minutes, 2% in both vertical and horizontal directions
It is preferable to set the following.

Intrinsic Viscosity of Film The intrinsic viscosity of the film of the present invention is 0.48 or more and 0.85 or more.
It is preferably less than. More preferably 0.58
And less than 0.80. If it exceeds 0.85, the viscosity of the film is high, so that it is difficult to crystallize and the perforated shape is not easily maintained. Conversely, if it is less than 0.48, the film-forming property becomes extremely difficult.

Melt Viscosity The melt viscosity of the film of the present invention must satisfy the following formula (1). 200 ≦ V (Tm + 20) −V (Tm + 40) ≦ 700 (1) (In the above formula (1), V (Tm + 20) is the film melting point +
The melt viscosity (poise) at a shear rate of 1000 sec ^-1 at 20 (° C.) and V (Tm + 40) represent the melt viscosity (poise) at a shear rate of 1000 sec ^-1 at a film melting point of +40 (° C.). )

The difference in the melt viscosity of the above formula (1) is preferably 300 to 700 (poise), more preferably 40.
0 to 600 (poise). 200 melt viscosity difference
If it is less than (poise), the thermal head is apt to be scummed at the time of perforation, causing white spots. Also, the perforation diameter tends to be large, the adjacent holes tend to stick together, and the printing becomes unclear. If it exceeds 700 (poise),
Since the polymer is hardly softened at the time of perforation, the pores are hardly spread, and high perforation sensitivity cannot be obtained. The melt viscosity difference can be in the range specified in the present invention by adjusting the type, copolymerization amount, and blending ratio of each polyester constituting the polyester composition.

Plane Orientation Coefficient The plane orientation coefficient (Ns) of the film of the present invention is 0.120.
It is necessary to be at least 0.145. It is preferably from 0.125 to 0.145, more preferably from 0.125 to 0.140. Ns is 0.12
If it is less than 0, the printing durability decreases, and if Ns exceeds 0.145, the film becomes brittle and it becomes impossible to form a film.

Porous Support A heat-sensitive stencil sheet can be produced by laminating a porous support on the film of the present invention. Examples of the porous support include, but are not particularly limited to, Japanese paper, Tengucho, synthetic fiber papermaking, various woven fabrics, and nonwoven fabrics. The basis weight of the porous support is not particularly limited, but is usually ^{2 to 20} g / m ² , preferably 5 to ²⁰ g / m ² .
15 g / m ² is used. When a mesh-like sheet is used, it is preferable to use a woven fiber having a thickness of 20 to 60 μm and a lattice spacing of 20 to 250 μm. The adhesive used for bonding the film and the porous support of the present invention is not particularly limited, and examples thereof include vinyl acetate-based resins, acrylic resins, urethane-based resins, and polyester-based resins. Can be.

[0026]

EXAMPLES Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to the following examples unless it exceeds the gist. In the present invention, various physical properties and characteristics are measured and defined as follows.

(1) Melting point of film 10 mg of film was added to TA Instruments Thermal Analyst 21.
Using a type 00, the film is heated at a rate of 20 ° C./min in a stream of N ₂ , and the endothermic behavior accompanying the melting of the film is analyzed by the first derivative, and melting is performed when the value of the first derivative becomes 0. Determined as peak temperature. When a shoulder peak was present in the range of the main melting peak, a point where the slope of the DSC curve was a valley of the first derivative curve in the positive region was determined as the shoulder temperature.

(2) Film Thickness The thickness t (μm) of the film is represented by W (c)
m), when the length was sampled to 1 (cm), the weight was G (g), and when the density was d (g / cm ³ ), calculation was performed by the following equation. t = 10000G / Wld

(3) Melt Viscosity Measurement The sample was dried at 150 ° C. for 4 hours using a flow tester CFT-500 manufactured by Shimadzu Corporation, and then the temperature was set based on the film melting point (Tm) determined by DSC measurement. (Tm + 20 ℃, Tm +
At 40 ° C.) and the melt viscosity (poise) at a shear rate of 1000 sec ⁻¹ was measured.

(4) Plane Orientation Coefficient Using an Abbe refractometer, the machine flow direction (n _MD ), the direction perpendicular to the machine plane direction (n _TD ) and the direction perpendicular to the machine plane (n _Z ) are used. The refractive index was measured, and the plane orientation coefficient Ns was calculated by the following equation. Ns = ( _nMD + _nTD ) / 2- _nz

(5) Evaluation of Character Printing (5-1) Evaluation of Character Sharpness A JIS first-level character was used as a manuscript having a character size of 2.0 mm square, and a porous support made of polyester gauze and heat-sensitive material were used. The film (the same applies to the examples and comparative examples) is bonded to the film, and the flash irradiation method is “RISO business card game”.
Using a plate making / printing machine (manufactured by Riso Kagaku Co., Ltd.)
Plates were made using RT VT-3950 (manufactured by Ricoh Co., Ltd.), and the printed ones were evaluated as follows. 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. The evaluation was performed in three stages of A, B, and C by the naked eye judgment. A is the same as the original, B is different from the original, and the line is partially cut or stuck but readable.
C is cut or turned to a state where it can hardly be read.

(5-2) Evaluation of Missing Characters The same plate making and printing as in (5-1) were performed, and the manner of missing characters was evaluated. Some of the obviously missing parts were marked as unusable and marked with a cross. In addition, it is not completely missing, but a slight (to the extent readable) is recognized.
Indicated by the mark. Those without any missing parts are indicated by a circle.

(5-3) Evaluation of Unevenness of Character Thickness A character having a character size of 5.0 mm □ was printed using the same plate making and printing machine as in (5-1), and the printed state was viewed with the inner eye. evaluated. Compared to the characters on the original, those having clearly unevenness in the thickness of the characters were marked with an X mark as having poor appearance and being unusable, and those having no unevenness in the thickness were marked with a circle as being usable and usable.

(5-4) Evaluation of Character Thickness Plate-making and printing were performed in the same manner as in (5-3), and changes in character thickness were visually evaluated. Compared with the thickness of the text of the manuscript, those which are clearly thicker or thinner are indicated by X as those which cannot be used, and those which have no change in thickness are indicated by ○. Also, it becomes slightly thicker,
Those that are thin or usable can be indicated by a triangle.

(6) Evaluation of solid printing (6-1) Evaluation of clarity of solid printing The same plate-making as described above using a black circle having a diameter of 1 to 5 mm (circled and blacked out inside) as an original. The printed matter was evaluated as follows. Judgment was made based on the unevenness (partial) of the outline based on the size of the original. Those with irregularities of 200 μm or more from the size of the original were poor in appearance and unclear, and were marked with “X”, and those with irregularities of 50 μm or less were sharp and indicated with “O”. The intermediate ones are indicated by a triangle.
Depending on how it is used, it can be used with △.

(6-2) Correspondence between solid printing and original size Printing is performed in the same manner as in (6-1), and printing is performed in all directions (0 ° and 180 °,
45 ° and 225 °, 90 ° and 270 °, 135 ° and 31
(At a position of 5 °), and the correspondence of the size with the size of the document was evaluated. 500 μm compared to original size
Differences (both large and small) that are different from the above were indicated by crosses as those having poor compatibility, and those having a size of 50 μm or less were indicated by ○ as those having good compatibility. The middle one
Although indicated by a mark, it can be used depending on the application.

(6-3) Evaluation of Light and Dark Spots in Solid Printing Printing was performed in the same manner as in (6-1), and the presence or absence of light and dark spots in solid printing was visually evaluated. Those with shading were indicated by x, and those without shading were indicated by o.

(7) Evaluation of Pattern Printing Using a checkerboard pattern of 6 × 6 1 cm squares shown in FIG. 1 as a manuscript, the same plate making and printing as described above were evaluated as follows. 4x4 at the center of the printed checkered pattern
The size of each cell in each cell was evaluated, and the correspondence between the size of the document and the size was evaluated. 50 compared to original size
In the case where there was at least one thing different from 0 μm or more (in some cases, it was large or small), it was indicated with a cross mark as having poor compatibility, and was shown with a circle as having good correspondence if it was 50 μm or less. The intermediate ones are indicated by a triangle, but can be used depending on the application. Further, even when the white background portion of the checkered pattern is stained by fading of the ink, it is also indicated by a cross.

(8) Evaluation of sensitivity Five kinds of pencil hardness of 5H, 4H, 3H, 2H and H were prepared, and a document in which characters were written with a pressing pressure of 130 g was used as a document. It was evaluated whether it could be done. 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.

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

(10) Evaluation of wrinkles The sample was divided into two parts, and one was bonded to a polyester gauze by an ordinary method. The other was slit to a width narrow enough to take an A4 plate, and both sides were carefully bonded with polyester gauze so as to minimize wrinkles by nipping both ends with a squeezing roller. The sensitivity evaluations of the two were compared, and if there was a difference, the degree of wrinkles was determined to be poor. ：: No difference ：: One step difference Δ: Two step difference ×: Difference of three or more steps

(11) Evaluation of Storage Property The laminated base paper was left in a gear oven at 60 ° C. for 2 hours, and then visually evaluated for wrinkles and curls, and judged according to the following criteria. ：: No practically hindered change occurred before and after standing. ×: Practical changes occurred before and after standing.

Types of polyester polymer As a polyester polymer, isophthalate is 5 mol
polyhexamethylene terephthalate copolymer having an intrinsic viscosity of 1.30 (PHMT / IA5
), Polybutylene terephthalate having an intrinsic viscosity of 0.90 (abbreviated as PBT), and 10 adipic acid.
Polybutylene terephthalate copolymer having an intrinsic viscosity of 0.90 copolymerized at a ratio of 1% (abbreviated as PBT / AA10), polybutylene having an intrinsic viscosity of 0.90 copolymerized with isophthalic acid at a ratio of 5 mol% Terephthalate copolymer (abbreviated as PBT / IA5), polybutylene terephthalate copolymer having an intrinsic viscosity of 0.90 and copolymerized with 2,6-naphthalenedicarboxylic acid at a ratio of 10, 20 mol% (PBT / NDC10, respectively) , PBT
/ NDC20), and 10% isophthalic acid
A polyethylene terephthalate copolymer having an intrinsic viscosity of 0.65 (abbreviated as PET / IA10) copolymerized at a ratio of mol% was used.

Example 1 Raw materials having the compositions shown in Table 1 were sufficiently dried, and then supplied to an extruder. The resin composition used was melt-extruded at 270 ° C., and the surface temperature was measured using an electrostatic application casting method. It was cooled and solidified by a casting drum at 20 ° C. to produce an unstretched film. This unstretched film is
At 70 ° C., 3.6 times in the vertical direction, and at 80 ° C., 3 times in the horizontal direction.
After successive biaxial stretching at a magnification of 9 times, the film was once cooled and then subjected to a heat treatment for 5 seconds while relaxing at 90 ° C. by 2% to obtain a thickness of 1.
A 6 μm biaxially stretched film was obtained. Table 1 shows the properties of the film. The biaxially stretched film thus obtained was bonded to polyester gauze (made of polyethylene terephthalate fiber) to prepare a heat-sensitive stencil sheet, which was evaluated by a plate-making / printing machine. The results are shown in Table 2. .

Example 2 A film having a thickness of 1.6 μm was prepared in the same manner as in Example 1 except that the heat treatment temperature was changed to 100 ° C., and then a heat-sensitive stencil sheet was prepared. Tables 1 and 2 show the evaluation results of the film and the printing base paper.

[Examples 3 and 4] The polyester composition was changed to the ratio shown in Table 1, and among the stretching conditions, the longitudinal stretching temperature was 50 ° C, the transverse stretching temperature was 55 ° C, and the heat treatment temperature was 110.
The thickness was 1.6 μm by the same manufacturing method as in Example 1 except that the temperature was changed to ° C.
And a heat-sensitive stencil sheet was prepared. Tables 1 and 2 show the evaluation results of the film and the printing base paper.

[Examples 5 and 6] The polyester composition was changed to the ratio shown in Table 1, and among the stretching conditions, the longitudinal stretching temperature was 65 ° C, the transverse stretching temperature was 75 ° C, and the heat treatment temperature was 115.
The thickness was 1.6 μm by the same manufacturing method as in Example 1 except that the temperature was changed to ° C.
And a heat-sensitive stencil sheet was prepared. Tables 1 and 2 show the evaluation results of the film and the printing base paper.

Example 7 The polyester composition was changed to the ratio shown in Table 1, and the heat treatment temperature was set at 120 among the stretching conditions.
The thickness was 1.6 μm by the same manufacturing method as in Example 1 except that the temperature was changed to ° C.
And a heat-sensitive stencil sheet was prepared. Tables 1 and 2 show the evaluation results of the film and the printing base paper.

[Comparative Example 1] The polyester composition was changed to the ratio shown in Table 1, and the longitudinal stretching temperature was set at 80 among the stretching conditions.
A film having a thickness of 1.6 μm was prepared by the same method as in Example 1 except that the temperature and the transverse stretching temperature were changed to 90 ° C., and then a heat-sensitive stencil sheet was prepared. Tables 1 and 2 show the evaluation results of the film and the printing base paper.

Comparative Example 2 The same manufacturing method as in Example 1 was used except that the polyester composition was changed to the ratio shown in Table 1, and the thickness was 1.6.
A .mu.m film was prepared, and then a thermosensitive stencil sheet was prepared. Tables 1 and 2 show the evaluation results of the film and the printing base paper.

Comparative Example 3 A film was prepared in the same manner as in Example 1 except that the thickness was changed to 7.1 μm, and then a heat-sensitive stencil sheet was prepared. Tables 1 and 2 show the evaluation results of the film and the printing base paper.

[0052]

[Table 1]

[0053]

[Table 2]

[0054]

The film for heat-sensitive stencil printing paper of the present invention exhibits the following excellent functions and effects. That is,
The base paper using the film can: (1) Clear plate making and printing can be performed for both characters and solid printing. (2) Plate making and printing without unevenness of thickness and shading can be performed by character and solid printing. (3) The sensitivity is remarkably high. Moreover, with an appropriate character density,
Excellent printing durability and appropriate consumption of ink. (4) High sensitivity can be stably obtained without wrinkles. (5) Less curl and excellent storage stability.

[Brief description of the drawings]

FIG. 1 is a checkered original used for pattern printing evaluation.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H114 AB25 BA01 BA06 DA56 DA64 DA73 EA03 EA05 EA10 FA02 FA06 FA09 4F071 AA44 AA45 AA46 AA84 AA88 AH12 AH16 BB06 BC01 4J002 CF05X CF06X CF07W CF08X GP00 GQ00 GT00

Claims (2)

[Claims] 1. A biaxially stretched polyester film having a thickness of 0.2 to 7.0 μm, comprising a polyester composition containing 40% by weight or more of a polybutylene terephthalate copolymer, and having a melting point (Tm) of the film. ) Is 18
0 ° C or higher and 230 ° C or lower, plane orientation coefficient (Ns) is 0.12
A heat-sensitive stencil film for base paper, characterized in that the melt viscosity satisfies the range of 0 to 0.145 and the melt viscosity satisfies the following formula (1). 200 ≦ V (Tm + 20) −V (Tm + 40) ≦ 700 (1) (In the above formula (1), V (Tm + 20) is the film melting point +
The melt viscosity (poise) at a shear rate of 1000 sec ^-1 at 20 (° C.) and V (Tm + 40) represent the melt viscosity (poise) at a shear rate of 1000 sec ^-1 at a film melting point of +40 (° C.). ) 2. The film for heat-sensitive stencil printing paper according to claim 1, wherein the melting point of the polybutylene terephthalate copolymer is from 180 ° C. to 220 ° C.