JPH08244372A - Film for paperless thermal stencil printing base sheet - Google Patents

Abstract

PURPOSE: To provide a film for a paperless thermal stencil printing base sheet which has excellent punch sensitivity and curl resistance, and has excellent resolution and density of an image at the time of printing. CONSTITUTION: A film for a paperless thermal stencil printing base sheet comprises a biaxially oriented film made of polyester resin having a melting point of 150 to 240 deg.C and a thickness of 1 to 30μm to simultaneously satisfy the formulae (1) to (4). S<=10... (1). F<=150... (2). 10<=S×F<=1500... (3). 0.02<=Ra<=0.3... (4). [in the formulae, S is heating shrinkage factor (5) of the film after treated for 10min at 100 deg.C, F is heating shrinkage stress (g/mm<2> ) of the film after it is treated at 100 deg.C for 10sec, and Ra is the center line average height (μm) on the surface of the film].

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a polyester film for paperless heat-sensitive stencil printing base paper. More specifically, the present invention relates to a film for paperless heat-sensitive stencil printing base paper, which has excellent perforation sensitivity and curl resistance due to its specific melting point and shrinkage characteristics, and has excellent image resolution and density during printing.

[0002]

2. Description of the Related Art Conventionally, as a base paper for heat-sensitive stencil printing, a thermoplastic resin film such as polyester laminated with a porous thin paper, or substantially only a thermoplastic film ( A film for paperless) heat-sensitive stencil printing base paper is known, and the film used for such an application is required to have the following characteristics.

(1) It is also excellent in handleability and productivity during film production and base paper production. Specifically, during film production, the stretchability is good, troubles such as breakage do not occur, and the winding property and slitting property are also good,
It is necessary that wrinkles do not occur during winding and that winding does not occur. Even when the base paper is prepared, it is necessary that the problems such as the unwinding of the film and the running of the film in the process do not occur.

(2) It has a strength and an elastic modulus sufficient to withstand the work of laminating with porous thin paper and printing. Curling should not occur due to such lamination conditions or changes in temperature and humidity during storage. If the curl becomes large, handling and handling of the stencil in the stencil printing machine become poor, causing problems such as clogging of the stencil.

(3) The thermal perforation sensitivity is good. That is,
It is necessary to have sufficient heat-shrinkability so that it can be melted with a small amount of heat and that perforations of an appropriate size can be obtained so that an image during printing becomes clear. (4) The thermal perforation sensitivity does not decrease even when the plate is made many times. That is, the release layer surfactant and silicone oil,
It is necessary that molten debris of the film does not adhere as dirt on the thermal head.

(5) Gradation of thermal perforation is good. When used as a base paper, if the portion other than the portion to be perforated is melted due to the influence of the perforations in the periphery, the gradation of the printed image becomes inferior, which is not preferable. That is, it is desired to have a thermal perforation property that allows the clearly distinguishable between the perforated portion and the non-perforated portion. Conventionally, as a film used for such a purpose, JP-A-62-282983,
JP-A-63-160895, JP-A-63-312
Various proposals have been made in Japanese Patent Application Laid-Open No. 192, Japanese Patent Application Laid-Open No. 3-30996, Japanese Patent Application Laid-Open No. 3-45720, Japanese Patent Application Laid-Open No. 6-320700, etc. However, all of the above problems could not be solved.

[0007]

Means for Solving the Problems The inventors of the present invention have made extensive studies in view of the above problems, and as a result, a biaxially oriented film made of a specific polyester having specific shrinkage characteristics is suitable for a paperless heat-sensitive stencil printing base paper. As a result, they have completed the present invention.

That is, the gist of the present invention is that the melting point is 150.
Thickness of 1 ~ 30μ made of polyester resin at ~ 240 ° C
A biaxially stretched film of m having the following formulas (1) to (4)
A film for paperless heat-sensitive stencil printing base paper, which satisfies both of

[0009]

## EQU2 ## S ≦ 10 (1) F ≦ 150 (2) 10 ≦ S × F ≦ 1500 (3) 0.02 ≦ Ra ≦ 0.3 (4) [In the above formula, S is the heat shrinkage rate (%) of the film after treatment at 100 ° C. for 10 minutes, F is the heat shrinkage stress (g / mm ² ) of the film after treatment at 100 ° C. for 10 seconds, and Ra is the film surface. Represents the center line average roughness (μm) of

Hereinafter, the present invention will be described in detail. The difunctional acid component of the polyester referred to in the present invention is mainly an aromatic dicarboxylic acid or an ester-forming derivative thereof, and specifically, as terephthalic acid, 2,6-naphthalenedicarboxylic acid and an ester-forming derivative thereof. Examples thereof include dimethyl terephthalate and dimethyl 2,6-naphthalenedicarboxylate, and among these, terephthalic acid and dimethyl terephthalate are preferable. As the glycol component, ethylene glycol, butylene glycol, propylene glycol, polyethylene glycol, 1,4
-Cyclohexanedimethanol and the like are mentioned, and among these, ethylene glycol and butylene glycol are preferable.

The polyester used in the present invention may be a polyester having the above aromatic dicarboxylic acid or its ester-forming derivative and the above alkylene glycol as starting materials, but is a copolymer containing two or more kinds of components. It is preferable. In addition to the above as the component to be copolymerized, for example, a diol component such as diethylene glycol, neopentyl glycol, or polyalkylene glycol,
Examples include dicarboxylic acid components such as adipic acid, sebacic acid, phthalic acid, and isophthalic acid, trimellitic acid, and pyromellitic acid.

The melting point of the polyester film of the present invention is
It is in the range of 150 to 240 ° C, preferably 160 to 230 ° C. When the melting point is higher than 240 ° C, the high perforation sensitivity that is the object of the present invention cannot be obtained, and when the melting point is lower than 150 ° C, the heat-resistant dimensional stability of the film is deteriorated, and the process for producing the base paper and the preservation of the base paper are suppressed. It is not preferable because curling occurs inside and the gradation of the printed image deteriorates.

The thickness of the film of the present invention is 1 to 30 μm,
It is preferably 3 to 20 μm. More preferably 5 to
It is 15 μm. When the film thickness is thin, the heat conduction distance is shortened, and the heat energy required at the time of perforation is also reduced, so that the perforation property is improved and the resolution and printing quality during printing are improved, but if the thickness is less than 1 μm, The rigidity is lowered and the transportability of the stencil sheet is deteriorated, which is not preferable. Further, if the thickness exceeds 30 μm, the perforation property is deteriorated and unevenness occurs during printing, which is not preferable.

The film of the present invention has a heat shrinkage ratio (S) of 10% or less, preferably 8% after being treated at 100 ° C. for 10 minutes.
It is below. When S is more than 10%, it is not preferable because unevenness of perforation is likely to occur when dot-shaped perforations are formed using a thermal head as a stencil sheet. The heat shrinkage stress (F) of the film of the present invention after being treated at 100 ° C. for 10 seconds is 150 g / mm ² or less, preferably 100 g / mm ² or less. If F exceeds 150 g / mm ² , unevenness in perforation occurs when dot-shaped perforations are formed using a thermal head, resulting in uneven thickness, uneven shading, or dimensional change, which is not preferable.

In order to obtain a film for paperless heat-sensitive base paper, which is the most important feature of the present invention and which gives good perforation with a low heat source and further has good curl resistance, in addition to the above-mentioned film characteristics, the shrinkage characteristics (heat shrinkage rate) are required. And heat shrinkage stress) is important. That is, the product of the heat shrinkage ratio and the heat shrinkage stress (S ×
F) is 10 to 1500. If the S × F value is less than 10, the force for expanding the holes at the time of perforation is insufficient, and perforations having a size large enough to obtain a clear image at the time of printing cannot be obtained, which is not preferable. The S × F value is 1500
If it exceeds, curling occurs due to temperature and humidity changes during storage,
It is not preferable because handling property and transportability of the base paper in the stencil printing machine become poor, troubles such as paper clogging occur, and uneven thickness, uneven density or dimensional change occur when punching with a thermal head.

The room temperature curl diameter and the 50 ° C. curl diameter are usually 18 mm or more, preferably 20 mm or more.
If the room temperature curl diameter and the 50 ° C. curl diameter are less than 18 mm, the transportability of the base paper in the stencil printing machine becomes poor, and problems such as clogging of the base paper tend to occur. Further, the ratio of the room temperature curl diameter to the 50 ° C. curl diameter is 1.0 to 2.0, preferably 1.0 to 1.7. If this value exceeds 2.0,
Curling tends to occur easily depending on the lamination conditions or changes in temperature and humidity during storage.

The film of the present invention has a roughened surface in order to improve the winding process during film production and workability during printing, or to prevent fusion between the thermal head and the film during thermal perforation. It is preferable to impart appropriate slipperiness to the film, and for that purpose, fine inert particles may be added. The fine inert particles used for such a purpose usually have an average particle size of 0.05 to 3.0.
The average particle size is 0.1 to 2.0 μm, and the particle size distribution value (r) is 1.4 or less. Average particle size is 0.05μ
If it is less than m, the winding property tends to be poor. When the average particle size exceeds 3.0 μm or the particle size distribution value (r) exceeds 1.5, the flatness of the film surface is impaired and heat transfer becomes uneven, resulting in uneven perforation and resolution. May be inferior or the print quality may be impaired.

The amount of particles added is usually 0.05 to 3% by weight, preferably 0.1 to 2% by weight. If the amount of particles added is less than 0.05% by weight, the winding properties tend to be poor. On the other hand, if the amount of particles added exceeds 3% by weight, the degree of roughening of the film surface is too large, resulting in uneven heat transfer, uneven perforation, poor resolution, and impaired print quality. There is a fear.

Examples of the inert particles that can be used in the present invention include silicon oxide, titanium oxide, zeolite, silicon nitride, boron nitride, celite, alumina, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, barium sulfate. , Calcium phosphate, lithium phosphate, magnesium phosphate, lithium fluoride, aluminum oxide, silicon oxide, titanium oxide, kaolin, talc, carbon black, silicon nitride, boron nitride and as described in JP-B-59-5216. Examples of the crosslinked polymer fine powder include, but are not limited to, these. At this time, the inert particles to be blended may be a single component, or two or more components may be used simultaneously.

The method of blending the inert particles with the polyester in the present invention is not particularly limited, but for example, a method of adding the inert particles to the polyester polymerization step,
Alternatively, a method of melt-kneading before forming into a film is preferably used. In the present invention, it is possible to obtain a film whose surface is appropriately roughened by the method as described above, but in order to further satisfy the workability, the resolution during printing, and the printing quality to a higher degree, the film surface Center line average roughness (Ra) is 0.02 to 0.3 μm, preferably 0.05
It is necessary to appropriately select the conditions so as to be in the range of 0.2 μm. Next, a method for producing the polyester film of the present invention will be described.

In the present invention, the polymer is supplied to a well-known melt extrusion apparatus typified by an extruder, and heated to a temperature equal to or higher than the melting point of the polymer to be melted. Then
The molten polymer is extruded from a slit-shaped die and rapidly cooled and solidified on a rotating cooling drum to a temperature not higher than the glass transition temperature to obtain a substantially amorphous unoriented sheet. In this case, in order to improve the flatness of the sheet, it is necessary to enhance the adhesion between the sheet and the rotary cooling drum, and the electrostatic application adhesion method and / or the liquid coating adhesion method are preferably adopted in the present invention.

The electrostatic application adhesion method referred to here is usually a method in which a linear electrode is provided on the upper surface side of the sheet in a direction orthogonal to the flow of the sheet, and a DC voltage of about 5 to 10 kV is applied to the electrode. This is a method of imparting an electrostatic charge to the sheet to improve the adhesion to the drum. In addition, the liquid application contact method is a method for improving the adhesion between the drum and the sheet by uniformly applying the liquid to the whole or part of the surface of the rotary cooling drum (for example, only the portions that contact both ends of the sheet). Is. In the present invention, both may be used in combination as required.

In the present invention, the sheet thus obtained is biaxially stretched to form a film. Specifically, the unstretched sheet is stretched 2 to 4 times in the machine direction at 20 to 100 ° C. and then stretched 2 to 4 times in the transverse direction to obtain a biaxially oriented film. To get More preferably, the unstretched sheet is first 20-
2 ~ 3 times at 80 ° C, 1.1 ~ at 40 ~ 100 ° C
Stretch 1.5 times. Then, in the transverse direction at 50-100 ° C for 2
The film is stretched 4 times to obtain a biaxially oriented film. It is also possible to simultaneously biaxially stretch the unstretched sheet so that the area ratio becomes 2 to 16 times.

The film thus obtained may be heat-treated, and if necessary, may be stretched again in the machine direction and / or the transverse direction before or after the heat treatment. In the present invention, in order to obtain a film having the above-mentioned heat shrinkage property, the stretching ratio is 2 times or more as an area ratio, the heat treatment after stretching is not substantially performed, or even if it is performed, it is 150 ° C. or less, and further, 120 ° C or less, heat treatment time is 1 second to 5
It is preferable that the film is stretched or fixed at a length of 30% or less per minute.

In the present invention, if necessary, an aliphatic metal salt, a phosphate ester ester surfactant, a fluid lubricant such as silicone oil, and a fusion preventing layer such as a fluorine compound may be provided on one or both sides of the polyester film. May be given.
In addition, curling, which is considered to be caused by the shrinkage of the film, may occur during a drying process in manufacturing a stencil printing base paper and during long-term storage in the summer. Therefore, when the obtained film is aged at 40 to 70 ° C. for 5 hours to 5 days, preferably at 50 to 60 ° C. for 12 hours to 3 days, the curl resistance in the environment becomes good. In addition,
In the present invention, about 10% by weight or less of another polymer (for example, polyethylene, polystyrene, polycarbonate, polysulfone, polyphenylene sulfide, polyamide, polyimide, etc.) can be contained with respect to the total amount of polyester used for film formation. Also, if necessary,
You may mix | blend additives, such as an antioxidant, a heat stabilizer, a lubricant, an antistatic agent, a dye, and a pigment.

[0026]

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to the following examples unless it exceeds the gist thereof. The physical property measuring methods used in the present invention are shown below. (1) Melting point Seiko Electronics Co., Ltd. differential calorimeter SSC580DS
It measured using C20 type. The DSC measurement conditions are as follows. That is, 10 mg of the sample film is used for DSC
Set it in the device and raise the temperature at a rate of 10 ° C / min.
The melting point was measured in the range of 00 ° C, and the melting point was measured as the apex of the melting endothermic peak. (2) Heat shrinkage rate (S) 10 in an oven kept at 100 ° C. in a tensionless state.
Heat treatment was performed for a minute, the lengths of the samples before and after the heat treatment were measured, and the heat shrinkage rate was calculated by the following formula.

[0027]

## EQU3 ## S (%) = {(L0-L1) / L0} × 100 (where L0 is the sample length before heat treatment and L1 is the sample length after heat treatment) 5 points in the longitudinal and transverse directions of the film Each was measured and the average value was calculated.

(3) Heat shrinkage stress (F) A film was cut into a strip having a width of 10 mm, one end was set to the chuck of the load detector and the other was set to the fixed chuck, and the gap between the chucks was set to 50 mm. Immerse the film in an oil bath at 100 ° C without applying an initial load,
The stress value was measured 10 seconds after the start of immersion. The heat shrinkage stress (g / mm ² ) was calculated from the cross-sectional area of the film before immersion.

(4) Average particle size of fine particles Centrifugal sedimentation type particle size distribution analyzer SA- manufactured by Shimadzu Corporation
The particle size was measured by a sedimentation method based on Stokes's resistance law using CP3 type. The value of 50% integrated (volume basis) in the equivalent spherical distribution of the particles obtained by the measurement was used as the average particle diameter.

(5) Center line average roughness (Ra) According to the method described in Japanese Industrial Standard JIS B0601, a surface roughness measuring device (SE-3 manufactured by Kosaka Laboratory Ltd.)
The center line average roughness (Ra) was determined using F). The tip radius of the stylus was 2 μm, the load was 30 mg, and the cutoff value was 0.08 mm.

(6) Curling at room temperature A stencil printing base paper obtained by coating a polyester film with a heat fusion preventing layer is cut into B4 size sheets, and the film surface is placed on a flat table and the curl diameter after 24 hours at 25 ° C. Was measured. (7) Curling at 50 ° C In the same manner as at the time of curling at room temperature, the film surface is placed on a flat table and the temperature is set at 50 ° C and the humidity is 90%.
The curl diameter after the weekly treatment was measured.

(8) Practical characteristics of heat-sensitive stencil printing base paper The stencil printing base paper prepared by the above method was applied with a thermal head at an applied energy of 0.09 mJ () and 0.
A character image and a 16-step gradation image were made at 12 mJ (). The perforated state of the gradation image area was observed with a microscope from the film side of the plate-making base paper, and the evaluation was made according to the following criteria. ◎: Predetermined perforation was performed reliably and the size of the perforation was sufficient, and very good ○: Prescribed perforation was performed almost reliably, the size of the perforation was sufficient, and Δ: Rarely the predetermined perforation was obtained There is a part that cannot be drilled or a part where the size of the perforation is insufficient x: There are many parts where the predetermined perforation cannot be obtained, and the size of the perforation is also insufficient, which is a practical problem.

Example 1 100 parts by weight of dimethyl terephthalate, 30 parts by weight of ethylene glycol, 28 parts by weight of 1,4-butanediol and 0.005 parts by weight of tetrabutyl titanate were placed in a reactor and the reaction start temperature was set to 160 ° C. The reaction temperature was gradually raised as the methanol was distilled off, and after 3 hours at 210 ° C.
And After 4 hours, 5 parts by weight of an ethylene glycol slurry containing 0.3 part by weight of crosslinked organic particles having an average particle size of 0.75 μm was added to the reaction mixture in which the transesterification reaction was substantially completed. Titanate 0.
005 parts by weight was added and polycondensation reaction was carried out for 4 hours. That is, the temperature was gradually raised from 210 ° C to 260 ° C. On the other hand, the pressure is gradually reduced from normal pressure, and finally becomes 0.
It was set to 3 mmHg. After 4 hours from the start of the reaction, the reaction was stopped and the polymer was discharged under nitrogen pressure to obtain a copolyester.

The polyester thus obtained was extruded into a sheet form from an extruder set at 265 ° C., and rapidly cooled and solidified by using an electrostatic applied cooling method in a rotary cooling drum set at a surface temperature of 30 ° C. to have a thickness of 36 μm. A substantially amorphous sheet was obtained. The obtained sheet was stretched at 65 ° C. in the longitudinal direction at 2.7 times and at 70 ° C. in the lateral direction at 2.7 times, and further heat-treated at 80 ° C. for 6 seconds to produce a biaxially oriented film having a thickness of 5 μm. . Next, a silicone emulsion (KM768 manufactured by Shin-Etsu Chemical Co., Ltd.) was applied to the obtained film as a heat-sealing preventive layer with a wire bar to prepare a stencil printing base paper and evaluated.

Example 2 The same procedure as in Example 1 was repeated except that 95 parts by weight of dimethyl terephthalate and 5 parts by weight of dimethyl isophthalate were used instead of 100 parts by weight of dimethyl terephthalate. Was created and evaluated.

Example 3 In Example 1, a substantially amorphous sheet having a thickness of 40 μm was obtained, and the sheet was subjected to 3.0 times in the longitudinal direction at 65 ° C. and 3.0 times in the transverse direction at 70 ° C. A stencil sheet was prepared and evaluated in the same manner as in Example 1 except that the film was stretched and further heat-treated at 80 ° C. for 6 seconds to produce a biaxially oriented film having a thickness of 5 μm.

Comparative Example 1 100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol were used as starting materials, 0.09 parts by weight of magnesium acetate / tetrahydrate as a catalyst was placed in a reactor, the reaction starting temperature was 150 ° C., and methanol was used. The reaction temperature was gradually raised with the evaporation of the above and the temperature was raised to 230 ° C. after 3 hours. After 4 hours, 0.3 g of cross-linked organic particles having an average particle size of 0.75 μm were added to the reaction mixture in which the transesterification reaction was substantially completed.
5 parts by weight of ethylene glycol slurry containing 1 part by weight was added, and 0.04 part of ethyl acid phosphate was added,
0.04 parts of antimony trioxide was added and a polycondensation reaction was carried out for 4 hours. That is, the temperature was gradually raised from 230 ° C to 280 ° C. On the other hand, the pressure gradually decreases from normal pressure,
Finally, it was set to 0.3 mmHg. After 4 hours from the start of the reaction, the reaction was stopped and the polymer was discharged under nitrogen pressure to produce polyester.

The above polyester was extruded in a sheet form from an extruder set at 280 ° C. and rapidly cooled and solidified by using an electrostatic cooling method in a rotary cooling drum set at a surface temperature of 30 ° C. to have a thickness of 36 μm. An amorphous sheet was obtained.
The obtained sheet was stretched 2.7 times in the longitudinal direction at 78 ° C. and 2.7 times in the transverse direction at 90 ° C. and further heat-treated at 230 ° C. for 6 seconds to produce a biaxially oriented film having a thickness of 5 μm. . Next, a silicone emulsion (KM768 manufactured by Shin-Etsu Chemical Co., Ltd.) was applied to the obtained film as a heat-sealing preventive layer with a wire bar to prepare a stencil printing base paper and evaluated.

Comparative Example 2 In Example 1, a substantially amorphous sheet having a thickness of 6 μm was obtained, and the sheet was increased in the longitudinal direction by 2.7 times at 65 ° C. and in the lateral direction by 2.7 times at 70 ° C. A stencil sheet was prepared and evaluated in the same manner as in Example 1 except that the film was stretched and further heat-treated at 80 ° C. for 6 seconds to produce a biaxially oriented film having a thickness of 0.8 μm.

Comparative Example 3 In Example 1, a substantially amorphous sheet having a thickness of 290 μm was obtained, and the sheet was grown 2.7 times at 65 ° C. in the machine direction.
The film was stretched in the transverse direction 2.7 times at 70 ° C and then at 80 ° C for 6 times.
A stencil sheet was prepared and evaluated in the same manner as in Example 1 except that a biaxially oriented film having a thickness of 40 μm was produced by heat treatment for seconds.

Comparative Example 4 In Example 1, a substantially amorphous sheet having a thickness of 36 μm was obtained, and the sheet was magnified 2.7 times at 75 ° C. in the longitudinal direction and 2.7 times at 80 ° C. in the lateral direction. A stencil sheet was prepared and evaluated in the same manner as in Example 1 except that the film was stretched and heat-treated at 85 ° C. for 6 seconds to produce a biaxially oriented film having a thickness of 5 μm.

Comparative Example 5 In Example 1, a substantially amorphous sheet having a thickness of 61 μm was obtained, and the sheet was magnified 3.5 times at 65 ° C. in the longitudinal direction and 3.5 times at 80 ° C. in the lateral direction. A stencil sheet was prepared and evaluated in the same manner as in Example 1 except that the film was stretched and heat-treated at 85 ° C. for 6 seconds to produce a biaxially oriented film having a thickness of 5 μm.

Comparative Example 6 In Example 1, a substantially amorphous sheet having a thickness of 68 μm was obtained, and the sheet was increased 3.7 times in the longitudinal direction at 65 ° C. and 3.7 times in the transverse direction at 80 ° C. A stencil sheet was prepared and evaluated in the same manner as in Example 1 except that the film was stretched and further heat-treated at 80 ° C. for 6 seconds to produce a biaxially oriented film having a thickness of 5 μm.

Comparative Example 7 In Example 1, except that 5 parts by weight of an ethylene glycol slurry containing 0.3 part by weight of crosslinked organic particles having an average particle size of 0.35 μm was added to the reaction mixture after completion of the transesterification reaction. In the same manner as in Example 1, a stencil sheet was prepared and evaluated.

COMPARATIVE EXAMPLE 8 In Example 1, 1.0 parts of calcium carbonate particles having an average particle size of 2.1 μm were added to the reaction mixture after completion of the transesterification reaction.
A stencil sheet was prepared and evaluated in the same manner as in Example 1 except that 10 parts by weight of an ethylene glycol slurry containing 10 parts by weight was added. The physical properties of the obtained film and the evaluation results of the base paper are summarized in Table 1 below.

[0046]

[Table 1]

[0047]

According to the present invention, it is possible to provide a film for paperless heat-sensitive stencil printing paper which is excellent in perforation sensitivity and curl resistance, and has excellent image resolution and density during printing, and the industrial value of the present invention is high. .

Claims (1)

[Claims] 1. A paperless heat-sensitive stencil which is a biaxially stretched film having a thickness of 1 to 30 μm and made of a polyester resin having a melting point of 150 to 240 ° C., which simultaneously satisfies the following formulas (1) to (4). Film for printing base paper. [Equation 1] S ≦ 10 (1) F ≦ 150 (2) 10 ≦ S × F ≦ 1500 (3) 0.02 ≦ Ra ≦ 0.3 (4) [In the above formula, S is the heat shrinkage rate (%) of the film after treatment at 100 ° C. for 10 minutes, F is the heat shrinkage stress (g / mm ² ) of the film after treatment at 100 ° C. for 10 seconds, and Ra is the film surface. Represents the center line average roughness (μm) of