JP4242545B2 - Film for heat-sensitive stencil printing paper - Google Patents

Description

【００５３】
【表２】

【００５４】
【発明の効果】
本発明の感熱孔版印刷原紙用フィルムは、次のような優れた作用効果を発現する。すなわち、該フィルムを用いた原紙は、
（１）文字およびベタ印刷のいずれにも鮮明な製版、印刷が可能である。
（２）文字およびベタ印刷で太さ斑、濃淡斑のない製版、印刷が可能である。
（３）感度が著るしく高い。しかも適切な文字濃度で、耐刷性に優れており、適切なインキの消費量である。
（４）皺が無く、安定して高感度を得られる。
（５）カールが少なく、保存性が優れている。
【図面の簡単な説明】
【図１】図１は模様印刷の評価に用いる市松模様の原稿である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a film for a heat-sensitive stencil sheet, and more particularly to a film for a heat-sensitive stencil sheet having high printing sensitivity, vivid printing, and excellent durability and storage stability.
[0002]
[Prior art]
In recent years, heat-sensitive stencil printing using a base paper to be perforated and made by receiving heat from pulse irradiation such as a xenon flash lamp, a thermal head, or a laser beam has attracted attention. The principle of this plate making method is described in, for example, Japanese Patent Publication No. 41-7623, Japanese Patent Application Laid-Open No. 55-103957, Japanese Patent Application Laid-Open No. 59-143679.
[0003]
Conventionally, as a base paper used for such heat-sensitive stencil printing, a heat-sensitive stencil base film and a porous support laminated with an adhesive or heat are used. As the heat-sensitive stencil base paper, both vinyl chloride and vinylidene chloride are used. A polymer film, a polypropylene film, a highly crystallized polyethylene terephthalate film is used, and a thin paper or a polyester bag has been used as a porous support. However, these have the following disadvantages.
-When vinyl chloride or vinylidene chloride copolymer film is used, letters after printing do not appear clearly.
・ Polypropylene and polyethylene terephthalate films provide clear text, but solid printing (symbols or graphics with large ink adhesion area) does not provide clear text.
・ Both colors appear in the printed part.
・ Partial unevenness in character thickness.
・ Sensitivity is poor and black thin letters do not appear.
・ When an amorphous polymer such as PET-G is used alone, the perforated diameter becomes too large and a large amount of ink is consumed. is there.
[0004]
In order to eliminate these drawbacks, Japanese Patent Application Laid-Open No. 62-149497 proposes the use of a film having a low crystal melting energy. However, there are manufacturing problems such as blocking when drying the polymer chip in the film manufacturing process, sticking of the longitudinally stretched film edge to the clip of the tenter-type transverse stretching machine, and the thermal head has a polymer softened when drilling. There is a problem in print quality, such as streak-like white spots caused by polymer deposits when it is easy to adhere and continuous plate making. In order to solve these problems, for example, in Japanese Patent No. 2507612, a film showing two or more melting peaks in DSC temperature rise measurement is proposed and put into practical use. However, in a printing machine for high-speed printing, The sensitivity as a heat-sensitive stencil printing base paper may be insufficient, and further improvement has been desired. Further, wrinkles are likely to occur as a heat-sensitive stencil sheet.
[0005]
[Problems to be solved by the invention]
The object of the present invention is to solve the above-mentioned problems, and the printing of letters and solid printing are both clear, there are no printed thickness spots, no shading spots, no wrinkles, durability and storage stability. An object of the present invention is to provide a film for heat-sensitive stencil printing paper that is excellent and can maintain printing sensitivity even when printing at high speed.
[0006]
[Means for Solving the Problems]
That is, the present invention is a biaxially stretched polyester film having a thickness of 0.2 to 7.0 μm, the film comprising a polyester composition containing 40% by weight or more of a polybutylene terephthalate copolymer, and the melting point (Tm ) Is 180 ° C. or higher and 230 ° C. or lower, the plane orientation coefficient (Ns) is 0.120 or higher and 0.145 or lower, and the melt viscosity satisfies the following formula (1): It is.
200 ≦ V (Tm + 20) −V (Tm + 40) ≦ 700 (1)
(In the above formula (1), V (Tm + 20) is the film melting point + 20 (° C.) shear rate 1000 sec.^-1Melt viscosity (poise), V (Tm + 40) is a film melting point + 40 (° C.) shear rate of 1000 sec.^-1It represents the melt viscosity (poise). )
Moreover, in the said structure, it is preferable that melting | fusing point of a polybutylene terephthalate copolymer is 180 degreeC or more and 220 degrees C or less.
[0007]
The heat-sensitive stencil sheet in the present invention is, as described above, perforated and made by perforation by receiving heat from a xenon flash lamp, a thermal head, a laser beam, etc. It is what was pasted together. When the film for thermal printing base paper (hereinafter sometimes simply referred to as thermal film) is irradiated with flash light or is brought into contact with a thermal head, portions such as characters and images on the printing base paper are perforated. The process of perforating the thermal film can be divided into the following three stages.
(1) A portion to which thermal energy is applied by contact with a thermal head or irradiation of electromagnetic waves (xenon flash lamp light, laser pulse, etc.) is softened and melted, and a hole can be triggered.
(2) Thermal energy is applied, and the polymer around the softened pores is thermally contracted by the diffused thermal energy to widen the pores.
(3) The softened polymer is attracted to the periphery of the hole by the heat shrinkage force, solidified by natural cooling / heat radiation, and the hole shape is maintained by forming the hole end.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Polyester composition
For the film of the present invention, a polyester composition containing 40% by weight or more of a polybutylene terephthalate copolymer is used. When the proportion of the polybutylene terephthalate copolymer is less than 40% by weight, the gradation is poor, the printing becomes unclear, and the printing sensitivity particularly during high-speed printing is not preferable. The 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, decanedicarboxylic acid, and the like, and examples of the alcohol component include ethylene glycol, diethylene glycol, Examples thereof include aliphatic diols such as trimethylene glycol and hexanediol, and alicyclic diols such as cyclohexanedimethanol. These may be used alone or in combination of two or more. Although the ratio of the copolymerization component depends on the type, a ratio in which the polymer melting point is in the range of 180 to 220 ° C. is preferable. When the polymer melting point is less than 180 ° C., the crystallinity is inferior, so that the tenter adheres to the clip so that a film cannot be formed. On the other hand, when the polymer melting point exceeds 220 ° C., the copolymer has a too high melting point, but the sensitivity during high-speed printing decreases. Here, the melting point of the copolyester is measured according to the method for measuring the melting point of the film.
[0009]
The polyester composition used in the present invention contains 60% by weight or less of a polyester other than the polybutylene terephthalate copolymer. Such a polyester is a thermoplastic polyester obtained by polycondensation of an acid component and a glycol component. As the acid component, 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, phenyl Indane dicarboxylic acid, diphenyl ether dicarboxylic acid, oxalic acid, succinic acid, adipic acid, suberic acid, sebacic acid, dodecanedioic acid, eicosandioic acid, dimer acid, 1,4-cyclohexanedicarboxylic acid, decalin dicarboxylic acid, hexahydroterephthalate Examples thereof include acids and ester-forming derivatives thereof. Examples of the glycol component include 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, bisphenol A ethylene oxide adduct, bisphenolsulfone ethylene oxide adduct, triethylene glycol, polyethylene oxide glycol, Examples thereof include polytetramethylene oxide glycol and neopentyl glycol. In addition, hydroxycarboxylic acids such as p-hydroxyethoxybenzoic acid and p-hydroxybenzoic acid and lower alkyl esters thereof can also be used.
[0010]
Further, the polyester may be one in which part or all of the terminal hydroxyl group and / or carboxyl group is blocked with a monofunctional compound such as benzoic acid or methoxypolyalkylene glycol, or for example, a very small amount. It may be modified with a trifunctional or higher functional ester-forming compound such as glycerin or pentaerythritol within a range where a substantially linear polymer is obtained.
[0011]
Among these, representative examples of the polyester include poly-2,6-naphthalenedicarboxylate and its copolymer, polyethylene terephthalate and its copolymer, polyhexamethylene terephthalate copolymer, and the like. In the present invention, it is preferable to use one or more polyesters selected from poly-2,6-naphthalenedicarboxylate and its copolymer, isophthalic acid copolymerized polyethylene terephthalate and polyhexamethylene terephthalate copolymer. Further, the polyester may contain a resin other than the polyester within a range not departing from the gist of the present invention.
[0012]
Melting point of film
The melting point of the film of the present invention needs to be 180 ° C. or higher and 230 ° C. or lower. If the film melting point is less than 180 ° C, the polymer softened at the time of perforation tends to adhere to the thermal head, and streaky white spots due to polymer deposits occur during continuous plate making. Occurs. In addition, it tends to be an image without gradation. In addition, the printing durability is lowered, which is not preferable. On the other hand, when the film melting point exceeds 230 ° C., the perforation sensitivity is lowered, which is not preferable.
[0013]
In addition, since the film of this invention consists of a polyester composition which consists of 2 or more types of polyester, two or more melting | fusing point of a film may be measured. In that case, the melting point of the highest temperature is defined as the melting point of the film. That is, in the present invention, the highest melting point of the film only needs to satisfy the above melting point range.
[0014]
Film melting point can be made into the range prescribed | regulated by this invention by adjusting the kind of each polyester which comprises a polyester composition, a copolymerization amount, and a mixture ratio. The film temperature can also be adjusted by the melt extrusion temperature at the time of film formation, the extruder residence time, and the like.
[0015]
In addition, the polyester composition in the present invention may contain organic or inorganic particles in order to improve the slipperiness of the film. In the present invention, if the average particle size of the additive particles is large, breakage tends to occur during film formation. The average particle diameter of the additive particles is preferably 3 μm or less, more preferably 2 μm or less. Further, for example, addition of a spherical lubricant such as spherical silica particles is preferable, and one type of the average particle size of the lubricant is about 1.5 ± 0.5 μm, and the other type is about 0.3 ± 0.2 μm. Two types of sizes are even more preferable.
[0016]
Furthermore, an additive having an absorption peak in the wavelength range of flash irradiation may be added to the polyester composition, and a lubricant and a surfactant may be added for the purpose of improving releasability from the base paper. good.
[0017]
Film production method
The film of the present invention may be added to the above-described polyester composition as desired, sufficiently dried, then supplied to an extruder, and melted from a slit die (for example, a T-die) or by an inflation cast method. After film formation, it is obtained by biaxial stretching. The biaxial stretching method is not particularly limited, and sequential biaxial stretching and simultaneous biaxial stretching (stenter method, tube method) can be used. In addition, the biaxially stretched film thus obtained may be appropriately heat-treated. The heat treatment conditions are not particularly limited, but it is usually performed in the range of 80 to 200 ° C. and a relaxation rate of 20% or less.
[0018]
The film of the present invention may be obtained by subjecting the film surface to corona discharge treatment in air, carbon dioxide gas or nitrogen gas in order to improve adhesion to the porous support.
[0019]
Film thickness
In the present invention, the thickness of the biaxially stretched film needs to be 0.2 to 7.0 μm, preferably 0.5 to 5.0 μm, and more preferably 0.8 to 3.5 μm. When the thickness is less than 0.2 μm, it becomes difficult to bond the porous support to the porous support, the printing is unclear, light and dark spots are likely to appear, and the printing durability is also lowered. On the other hand, when the thickness exceeds 7.0 μm, the sensitivity is low, and a missing portion is formed in the printing or the thickness becomes uneven.
[0020]
Thermal shrinkage of film
In the film of the present invention, the heat shrinkage rate after heat treatment at 100 ° C. for 10 minutes is preferably 10 to 25%, more preferably 12 to 23% in both the longitudinal direction heat shrinkage rate (SMD) and the transverse direction heat shrinkage rate (STD). . If the heat shrinkage rate is less than 10%, the plate making sensitivity of the film is deteriorated, which may cause a practical problem. On the other hand, if it exceeds 25%, it is difficult to maintain the shape of the holes, which is not preferable because of excessive ink consumption. Also, in order to prevent wrinkles and curling due to unexpected high temperatures (50 ° C or higher) during storage of heat-sensitive stencil paper, the thermal shrinkage ratio after heat treatment at 50 ° C for 120 minutes is 2% or less in both the vertical and horizontal directions. It is preferable to make it.
[0021]
Intrinsic viscosity of film
The intrinsic viscosity of the film of the present invention is preferably 0.48 or more and less than 0.85. More preferably, it is 0.58 or more and less than 0.80. If it exceeds 0.85, since the viscosity of the film is high, it becomes difficult to crystallize, and the maintenance of the perforated shape becomes worse. On the other hand, if it is less than 0.48, the film forming property becomes extremely difficult.
[0022]
Melt viscosity
The melt viscosity of the film of the present invention needs to 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 + 20 (° C.) shear rate 1000 sec.^-1Melt viscosity (poise), V (Tm + 40) is a film melting point + 40 (° C.) shear rate of 1000 sec.^-1It represents the melt viscosity (poise). )
[0023]
The melt viscosity difference of the above formula (1) is preferably 300 to 700 (poise), more preferably 400 to 600 (poise). If the difference in melt viscosity is less than 200 (poise), the thermal head is likely to be faint when drilling, which causes white spots. Also, the diameter of the perforations tends to be large, the adjacent holes are likely to stick together, and the printing becomes unclear. If it exceeds 700 (poise), the polymer is difficult to soften at the time of drilling, so that the hole is difficult to expand, and high drilling sensitivity cannot be obtained. The difference in melt viscosity can be within the range specified in the present invention by adjusting the type, copolymerization amount, and blending ratio of each polyester constituting the polyester composition.
[0024]
Planar orientation coefficient
The plane orientation coefficient (Ns) of the film of the present invention needs to be 0.120 or more and 0.145 or less. Preferably they are 0.125 or more and 0.145 or less, More preferably, they are 0.125 or more and 0.140 or less. When Ns is less than 0.120, the printing durability is lowered, and when Ns exceeds 0.145, the film becomes brittle and cannot be formed.
[0025]
Porous support
A heat-sensitive stencil sheet can be produced by laminating a porous support to the film of the present invention. The porous support is not particularly limited, and representative examples thereof include Japanese paper, shingu, synthetic fiber paper, various woven fabrics, and non-woven fabrics. The basis weight of the porous support is not particularly limited, but is usually 2 to 20 g / m.², Preferably 5 to 15 g / m²Is used. When a mesh sheet is used, it is preferable to use a woven fiber having a thickness of 20 to 60 [mu] m and a lattice spacing of 20 to 250 [mu] m. Although it does not specifically limit as an adhesive agent used for bonding the film of this invention and a porous support body, A vinyl acetate resin, an acrylic resin, a urethane resin, and a polyester resin are mentioned as the representative example. Can do.
[0026]
【Example】
EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated still in detail, this invention is not limited to a following example, unless the summary is exceeded. Various physical property values and characteristics in the present invention are measured and defined as follows.
[0027]
(1) Melting point of film
10 mg of film using TA Instruments Thermal Analyst 2100 type, N₂The film was heated in an air stream at a heating rate of 20 ° C./min, the endothermic behavior accompanying the melting of the film was analyzed by a first derivative, and the point where the value of the first derivative was 0 was determined as the melting peak temperature. Further, when the shoulder melting peak was present in the range of the main melting peak, the shoulder temperature was determined so that the slope of the DSC curve was a valley of the first derivative curve in the positive region.
[0028]
(2) Film thickness
The thickness t (μm) of the film is W (cm) for the width of the film, G (g) for the sampled length of l (cm), and d (g / cm) for the density.^Three) And calculated by the following formula.
t = 10000G / Wld
[0029]
(3) Melt viscosity measurement
Using a flow tester CFT-500 manufactured by Shimadzu Corporation, the sample was dried at 150 ° C. for 4 hours, and then the set temperature (Tm + 20 ° C., Tm + 40) based on the film melting point (Tm) determined by DSC measurement. At a shear rate of 1000 sec.^-1The melt viscosity was measured.
[0030]
(4) Plane orientation coefficient
Using an Abbe refractometer, the machine flow direction (n_MD), The direction perpendicular to the drawing plane (n_TD) And the direction perpendicular to the stretched surface (n_Z) Was measured, and the plane orientation coefficient Ns was calculated by the following formula.
Ns = (n_MD+ N_TD) / 2-n_Z
[0031]
(5) Evaluation of character printing
(5-1) Evaluation of character clarity
A JIS first-level character is a manuscript with a character size of 2.0 mm □, and a porous support made of polyester wrinkles and a heat-sensitive film (same as in Examples and Comparative Examples) are combined. As the irradiation method, “RISO Business Card Pretend” plate making and printing machine (made by Riso Kagaku Co., Ltd.) is used, and as the thermal head perforation method, digital printing machine PRIPORT VT-3950 (made by Ricoh Co., Ltd.) is used. The printed materials were evaluated as follows. In addition, final evaluation showed the worse one of the evaluation result of a flash irradiation punching method and a thermal head punching method in each Example and the comparative example. The evaluation is made with three stages A, B, and C with the naked eye judgment. A is the same as the original, B is different from the original, but the lines are partially cut or stuck, but can be read, C is It has been cut or attached to a state that is hardly readable.
[0032]
(5-2) Evaluation of missing characters
Plate making and printing were performed in the same manner as in (5-1), and character missing was evaluated. Those clearly lacking were marked as unusable and marked with a cross. Moreover, although it is not a complete omission state, the thing which omission is recognized slightly (in the legible range) was shown by (triangle | delta) mark. Those with no missing part are marked with a circle.
[0033]
(5-3) Evaluation of thickness variation of characters
Characters with a character size of 5.0 mm □ were printed using the same plate making and printing machine as in (5-1), and the printed state was evaluated with the internal eye. Compared with the text of the manuscript, those marked with thick spots were marked with an X mark as being unusable and those with no thick spots were marked with a good appearance and usable.
[0034]
(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 evaluated with the naked eye. Compared with the thickness of the text of the manuscript, those that were clearly thicker or thinner were marked with an x mark as being unusable, and those with no change in thickness were marked with a mark. In addition, those which are slightly thicker or thinner but usable are indicated by Δ.
[0035]
(6) Evaluation of solid printing
(6-1) Evaluation of clearness of solid printing
Using a black circle having a diameter of 1 to 5 mm (a circle with the inside blackened) as a document, the same plate making and printing as described above were evaluated as follows. Judging from the size of the document as a reference, it was determined by the unevenness (partial) of the contour. Those with irregularities of 200 μm or more from the size of the document were marked with poor appearance and marked with x, and those with irregularities of 50 μm or less were marked with ◯. The intermediate one is indicated by Δ. Depending on how it is used, △ can also be used.
[0036]
(6-2) Compatibility with solid print original size
Print in the same manner as in (6-1), evaluate the sizes in all directions (0 ° and 180 °, 45 ° and 225 °, 90 ° and 270 °, 135 ° and 315 °), and the size of the document The correspondence of the size was evaluated. Those with a difference of 500 μm or more compared to the document size (sometimes large and small) are indicated by “x” as poor correspondence, and those below 50 μm are indicated by “◯” as good correspondence. An intermediate one is indicated by Δ, but it can be used depending on the application.
[0037]
(6-3) Evaluation of solid spots of solid printing
Printing was carried out in the same manner as in (6-1), and it was evaluated with the naked eye whether there were solid or dark spots of solid printing. Those with light and dark spots were indicated by x, and those without were indicated by ◯.
[0038]
(7) Evaluation of pattern printing
Using the checkered pattern in which 6 × 6 1 cm squares shown in FIG. 1 are collected as a manuscript, the same plate making and printing as described above were evaluated as follows. The size of each of the 4 × 4 squares in the center of the printed checkerboard pattern was evaluated, and the correspondence of the size with the size of the original was evaluated. If there is at least one thing that differs by 500 μm or more compared to the original size (sometimes large or small), it is indicated as “X” as a poor correspondence, and “○” is indicated as a good correspondence at 50 μm or less. It was. An intermediate one is indicated by Δ, but it can be used depending on the application. In addition, when a checkered white background portion is stained by ink fading, it is indicated by a cross.
[0039]
(8) Evaluation of sensitivity
Five types of pencil hardness 5H, 4H, 3H, 2H, and H were prepared, and a character was written with a pressing pressure of 130 g. The document was used to evaluate whether the character could be read. It is determined that the most light-colored character written in 5H can be read with the highest sensitivity, and the character written with a darker pencil can be read with lower sensitivity.
[0040]
(9) Durability evaluation
It was represented by the number of sheets that could be printed before the heat-sensitive film was damaged by the above-mentioned printing press (hereinafter referred to as the number of printing durability).
[0041]
(10) Evaluation of bag
The sample was divided into two, and one was bonded to a polyester bag by a conventional method. The other was slit so narrow that an A4 size plate could be taken, and both sides were niped with a widening roller and carefully bonded to a polyester wrinkle so as not to get wrinkles as much as possible. Both sensitivity evaluations were compared, and those with differences were judged to have poor wrinkles.
◎: No difference
○: 1 level difference
Δ: Difference is 2 steps
×: Difference is 3 or more
[0042]
(11) Evaluation of storage stability
After the laminated base paper was left in a gear oven at 60 ° C. for 2 hours, wrinkles and curls were visually evaluated and judged according to the following criteria.
○: No change that had any practical problems before and after leaving.
X: A change that had a practical problem before and after being left unattended.
[0043]
Types of polyester polymer
As a polyester polymer, a polyhexamethylene terephthalate copolymer having an intrinsic viscosity of 1.30 (abbreviated as PHMT / IA5) in which isophthalate is copolymerized at a ratio of 5 mol%, polybutylene terephthalate having an intrinsic viscosity of 0.90 (PBT and (Abbreviated), polybutylene terephthalate copolymer (abbreviated as PBT / AA10) having an intrinsic viscosity of 0.90 copolymerized with adipic acid in a proportion of 10 mol%, inherent in which isophthalic acid was copolymerized in a proportion of 5 mol% A polybutylene terephthalate copolymer having a viscosity of 0.90 (abbreviated as PBT / IA5) and a polybutylene terephthalate copolymer having an intrinsic viscosity of 0.90, each copolymerized with 2,20-naphthalenedicarboxylic acid at a ratio of 10, 20 mol%. Polymers (PBT / NDC10 and PBT / NDC20, respectively) To), and isophthalic acid was used polyethylene terephthalate copolymer having an intrinsic viscosity of 0.65 was copolymerized in a proportion of 10 mol% of (abbreviated as PET / IA10).
[0044]
[Example 1]
After sufficiently drying the raw material resin having the composition shown in Table 1, it is supplied to an extruder, the used resin composition is melt-extruded at 270 ° C., and cooled by a casting drum having a surface temperature of 20 ° C. using an electrostatic application casting method. Solidified to make an unstretched film. This unstretched film was sequentially biaxially stretched at a magnification of 3.6 times in the longitudinal direction at 70 ° C. and 3.9 times in the transverse direction at 80 ° C., and then cooled once and then 2% at 90 ° C. Heat treatment was applied for 5 seconds while relaxing to obtain a biaxially stretched film having a thickness of 1.6 μm. The properties of the film are shown in Table 1. The biaxially stretched film thus obtained was bonded to a polyester bag (made of polyethylene terephthalate fiber) to prepare a heat-sensitive stencil sheet, which was evaluated by applying it to a plate making / printing machine. The results are shown in Table 2. .
[0045]
[Example 2]
A film having a thickness of 1.6 μm was prepared by the same manufacturing method as in Example 1 except that the heat treatment temperature was set 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.
[0046]
[Example 3, Example 4]
The polyester composition was changed to the ratio shown in Table 1, and among the stretching conditions, the longitudinal stretching temperature was changed to 50 ° C, the transverse stretching temperature was changed to 55 ° C, and the heat treatment temperature was changed to 110 ° C. A 6 μm film was prepared, 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.
[0047]
[Example 5, Example 6]
The polyester composition was changed to the ratio shown in Table 1, and among the stretching conditions, the thickness was 1 in the same production method as in Example 1 except that the longitudinal stretching temperature was 65 ° C, the transverse stretching temperature was 75 ° C, and the heat treatment temperature was 115 ° C. A 6 μm film was prepared, 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.
[0048]
[Example 7]
The polyester composition was changed to the ratio shown in Table 1, and a film having a thickness of 1.6 μm was prepared by the same manufacturing method as in Example 1 except that the heat treatment temperature was changed to 120 ° C. among the stretching conditions. Created. Tables 1 and 2 show the evaluation results of the film and the printing base paper.
[0049]
[Comparative Example 1]
The polyester composition was changed to the ratio shown in Table 1, and a film having a thickness of 1.6 μm was produced by the same production method as in Example 1 except that the longitudinal stretching temperature was changed to 80 ° C. and the transverse stretching temperature was changed to 90 ° C. Then, a heat-sensitive stencil sheet was prepared. Tables 1 and 2 show the evaluation results of the film and the printing base paper.
[0050]
[Comparative Example 2]
A film having a thickness of 1.6 μm was prepared by the same manufacturing method as in Example 1 except that the polyester composition was changed to the ratio shown in Table 1, 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.
[0051]
[Comparative Example 3]
A film was prepared by the same production method as in Example 1 except that the thickness was 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 invention's effect】
The film for heat-sensitive stencil printing base paper of the present invention exhibits the following excellent effects. That is, the base paper using the film is
(1) Clear plate-making and printing are possible for both characters and solid printing.
(2) Plate making and printing without thickness spots and shading spots are possible by printing letters and solids.
(3) The sensitivity is remarkably high. Moreover, it has an appropriate character density, excellent printing durability, and an appropriate ink consumption.
(4) There is no wrinkle and high sensitivity can be obtained stably.
(5) Less curling and excellent storage.
[Brief description of the drawings]
FIG. 1 is a checkered original used for evaluation of pattern printing.

Claims (2)

A biaxially stretched polyester film having a thickness of 0.2 to 7.0 μm, the film comprising a polyester composition containing 40% by weight or more of a polybutylene terephthalate copolymer, and a melting point (Tm) of the film of 180 ° C. or more. 230.degree. C. or less, a plane orientation coefficient (Ns) of 0.120 or more and 0.145 or less, and a melt viscosity satisfying 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 melt viscosity (poise) at a shear rate of 1000 sec ⁻¹ at the film melting point + 20 (° C.), and V (Tm + 40) is a shear rate of 1000 sec ⁻ at the film melting point + 40 (° C.). Represents melt viscosity in ¹ ) The film for heat-sensitive stencil printing paper according to claim 1, wherein the polybutylene terephthalate copolymer has a melting point of 180 ° C or higher and 220 ° C or lower.

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